linux-stable/include/linux/ww_mutex.h

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 14:07:57 +00:00
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance
*
* Original mutex implementation started by Ingo Molnar:
*
* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*
* Wait/Die implementation:
* Copyright (C) 2013 Canonical Ltd.
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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* Choice of algorithm:
* Copyright (C) 2018 WMWare Inc.
*
* This file contains the main data structure and API definitions.
*/
#ifndef __LINUX_WW_MUTEX_H
#define __LINUX_WW_MUTEX_H
#include <linux/mutex.h>
#include <linux/rtmutex.h>
#if defined(CONFIG_DEBUG_MUTEXES) || \
(defined(CONFIG_PREEMPT_RT) && defined(CONFIG_DEBUG_RT_MUTEXES))
#define DEBUG_WW_MUTEXES
#endif
#ifndef CONFIG_PREEMPT_RT
#define WW_MUTEX_BASE mutex
#define ww_mutex_base_init(l,n,k) __mutex_init(l,n,k)
#define ww_mutex_base_is_locked(b) mutex_is_locked((b))
#else
#define WW_MUTEX_BASE rt_mutex
#define ww_mutex_base_init(l,n,k) __rt_mutex_init(l,n,k)
#define ww_mutex_base_is_locked(b) rt_mutex_base_is_locked(&(b)->rtmutex)
#endif
struct ww_class {
atomic_long_t stamp;
struct lock_class_key acquire_key;
struct lock_class_key mutex_key;
const char *acquire_name;
const char *mutex_name;
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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unsigned int is_wait_die;
};
struct ww_mutex {
struct WW_MUTEX_BASE base;
struct ww_acquire_ctx *ctx;
#ifdef DEBUG_WW_MUTEXES
struct ww_class *ww_class;
#endif
};
struct ww_acquire_ctx {
struct task_struct *task;
unsigned long stamp;
unsigned int acquired;
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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unsigned short wounded;
unsigned short is_wait_die;
#ifdef DEBUG_WW_MUTEXES
unsigned int done_acquire;
struct ww_class *ww_class;
void *contending_lock;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
unsigned int deadlock_inject_interval;
unsigned int deadlock_inject_countdown;
#endif
};
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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#define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die) \
{ .stamp = ATOMIC_LONG_INIT(0) \
, .acquire_name = #ww_class "_acquire" \
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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, .mutex_name = #ww_class "_mutex" \
, .is_wait_die = _is_wait_die }
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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#define DEFINE_WD_CLASS(classname) \
struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1)
#define DEFINE_WW_CLASS(classname) \
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
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struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0)
/**
* ww_mutex_init - initialize the w/w mutex
* @lock: the mutex to be initialized
* @ww_class: the w/w class the mutex should belong to
*
* Initialize the w/w mutex to unlocked state and associate it with the given
* class. Static define macro for w/w mutex is not provided and this function
* is the only way to properly initialize the w/w mutex.
*
* It is not allowed to initialize an already locked mutex.
*/
static inline void ww_mutex_init(struct ww_mutex *lock,
struct ww_class *ww_class)
{
ww_mutex_base_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key);
lock->ctx = NULL;
#ifdef DEBUG_WW_MUTEXES
lock->ww_class = ww_class;
#endif
}
/**
* ww_acquire_init - initialize a w/w acquire context
* @ctx: w/w acquire context to initialize
* @ww_class: w/w class of the context
*
* Initializes an context to acquire multiple mutexes of the given w/w class.
*
* Context-based w/w mutex acquiring can be done in any order whatsoever within
* a given lock class. Deadlocks will be detected and handled with the
* wait/die logic.
*
* Mixing of context-based w/w mutex acquiring and single w/w mutex locking can
* result in undetected deadlocks and is so forbidden. Mixing different contexts
* for the same w/w class when acquiring mutexes can also result in undetected
* deadlocks, and is hence also forbidden. Both types of abuse will be caught by
* enabling CONFIG_PROVE_LOCKING.
*
* Nesting of acquire contexts for _different_ w/w classes is possible, subject
* to the usual locking rules between different lock classes.
*
* An acquire context must be released with ww_acquire_fini by the same task
* before the memory is freed. It is recommended to allocate the context itself
* on the stack.
*/
static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
struct ww_class *ww_class)
{
ctx->task = current;
ctx->stamp = atomic_long_inc_return_relaxed(&ww_class->stamp);
ctx->acquired = 0;
locking: Implement an algorithm choice for Wound-Wait mutexes The current Wound-Wait mutex algorithm is actually not Wound-Wait but Wait-Die. Implement also Wound-Wait as a per-ww-class choice. Wound-Wait is, contrary to Wait-Die a preemptive algorithm and is known to generate fewer backoffs. Testing reveals that this is true if the number of simultaneous contending transactions is small. As the number of simultaneous contending threads increases, Wait-Wound becomes inferior to Wait-Die in terms of elapsed time. Possibly due to the larger number of held locks of sleeping transactions. Update documentation and callers. Timings using git://people.freedesktop.org/~thomash/ww_mutex_test tag patch-18-06-15 Each thread runs 100000 batches of lock / unlock 800 ww mutexes randomly chosen out of 100000. Four core Intel x86_64: Algorithm #threads Rollbacks time Wound-Wait 4 ~100 ~17s. Wait-Die 4 ~150000 ~19s. Wound-Wait 16 ~360000 ~109s. Wait-Die 16 ~450000 ~82s. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@kernel.org>
2018-06-15 08:17:38 +00:00
ctx->wounded = false;
ctx->is_wait_die = ww_class->is_wait_die;
#ifdef DEBUG_WW_MUTEXES
ctx->ww_class = ww_class;
ctx->done_acquire = 0;
ctx->contending_lock = NULL;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
debug_check_no_locks_freed((void *)ctx, sizeof(*ctx));
lockdep_init_map(&ctx->dep_map, ww_class->acquire_name,
&ww_class->acquire_key, 0);
mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_);
#endif
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
ctx->deadlock_inject_interval = 1;
ctx->deadlock_inject_countdown = ctx->stamp & 0xf;
#endif
}
/**
* ww_acquire_done - marks the end of the acquire phase
* @ctx: the acquire context
*
* Marks the end of the acquire phase, any further w/w mutex lock calls using
* this context are forbidden.
*
* Calling this function is optional, it is just useful to document w/w mutex
* code and clearly designated the acquire phase from actually using the locked
* data structures.
*/
static inline void ww_acquire_done(struct ww_acquire_ctx *ctx)
{
#ifdef DEBUG_WW_MUTEXES
lockdep_assert_held(ctx);
DEBUG_LOCKS_WARN_ON(ctx->done_acquire);
ctx->done_acquire = 1;
#endif
}
/**
* ww_acquire_fini - releases a w/w acquire context
* @ctx: the acquire context to free
*
* Releases a w/w acquire context. This must be called _after_ all acquired w/w
* mutexes have been released with ww_mutex_unlock.
*/
static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
2019-09-19 16:09:40 +00:00
mutex_release(&ctx->dep_map, _THIS_IP_);
#endif
#ifdef DEBUG_WW_MUTEXES
DEBUG_LOCKS_WARN_ON(ctx->acquired);
tree-wide: replace config_enabled() with IS_ENABLED() The use of config_enabled() against config options is ambiguous. In practical terms, config_enabled() is equivalent to IS_BUILTIN(), but the author might have used it for the meaning of IS_ENABLED(). Using IS_ENABLED(), IS_BUILTIN(), IS_MODULE() etc. makes the intention clearer. This commit replaces config_enabled() with IS_ENABLED() where possible. This commit is only touching bool config options. I noticed two cases where config_enabled() is used against a tristate option: - config_enabled(CONFIG_HWMON) [ drivers/net/wireless/ath/ath10k/thermal.c ] - config_enabled(CONFIG_BACKLIGHT_CLASS_DEVICE) [ drivers/gpu/drm/gma500/opregion.c ] I did not touch them because they should be converted to IS_BUILTIN() in order to keep the logic, but I was not sure it was the authors' intention. Link: http://lkml.kernel.org/r/1465215656-20569-1-git-send-email-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Stas Sergeev <stsp@list.ru> Cc: Matt Redfearn <matt.redfearn@imgtec.com> Cc: Joshua Kinard <kumba@gentoo.org> Cc: Jiri Slaby <jslaby@suse.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Borislav Petkov <bp@suse.de> Cc: Markos Chandras <markos.chandras@imgtec.com> Cc: "Dmitry V. Levin" <ldv@altlinux.org> Cc: yu-cheng yu <yu-cheng.yu@intel.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Brian Gerst <brgerst@gmail.com> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Will Drewry <wad@chromium.org> Cc: Nikolay Martynov <mar.kolya@gmail.com> Cc: Huacai Chen <chenhc@lemote.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> Cc: Rafal Milecki <zajec5@gmail.com> Cc: James Cowgill <James.Cowgill@imgtec.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Alex Smith <alex.smith@imgtec.com> Cc: Adam Buchbinder <adam.buchbinder@gmail.com> Cc: Qais Yousef <qais.yousef@imgtec.com> Cc: Jiang Liu <jiang.liu@linux.intel.com> Cc: Mikko Rapeli <mikko.rapeli@iki.fi> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Brian Norris <computersforpeace@gmail.com> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: "Luis R. Rodriguez" <mcgrof@do-not-panic.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Kalle Valo <kvalo@qca.qualcomm.com> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Tony Wu <tung7970@gmail.com> Cc: Huaitong Han <huaitong.han@intel.com> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Juergen Gross <jgross@suse.com> Cc: Jason Cooper <jason@lakedaemon.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrea Gelmini <andrea.gelmini@gelma.net> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Rabin Vincent <rabin@rab.in> Cc: "Maciej W. Rozycki" <macro@imgtec.com> Cc: David Daney <david.daney@cavium.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-03 20:45:50 +00:00
if (!IS_ENABLED(CONFIG_PROVE_LOCKING))
/*
* lockdep will normally handle this,
* but fail without anyway
*/
ctx->done_acquire = 1;
tree-wide: replace config_enabled() with IS_ENABLED() The use of config_enabled() against config options is ambiguous. In practical terms, config_enabled() is equivalent to IS_BUILTIN(), but the author might have used it for the meaning of IS_ENABLED(). Using IS_ENABLED(), IS_BUILTIN(), IS_MODULE() etc. makes the intention clearer. This commit replaces config_enabled() with IS_ENABLED() where possible. This commit is only touching bool config options. I noticed two cases where config_enabled() is used against a tristate option: - config_enabled(CONFIG_HWMON) [ drivers/net/wireless/ath/ath10k/thermal.c ] - config_enabled(CONFIG_BACKLIGHT_CLASS_DEVICE) [ drivers/gpu/drm/gma500/opregion.c ] I did not touch them because they should be converted to IS_BUILTIN() in order to keep the logic, but I was not sure it was the authors' intention. Link: http://lkml.kernel.org/r/1465215656-20569-1-git-send-email-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Stas Sergeev <stsp@list.ru> Cc: Matt Redfearn <matt.redfearn@imgtec.com> Cc: Joshua Kinard <kumba@gentoo.org> Cc: Jiri Slaby <jslaby@suse.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Borislav Petkov <bp@suse.de> Cc: Markos Chandras <markos.chandras@imgtec.com> Cc: "Dmitry V. Levin" <ldv@altlinux.org> Cc: yu-cheng yu <yu-cheng.yu@intel.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Brian Gerst <brgerst@gmail.com> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Will Drewry <wad@chromium.org> Cc: Nikolay Martynov <mar.kolya@gmail.com> Cc: Huacai Chen <chenhc@lemote.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> Cc: Rafal Milecki <zajec5@gmail.com> Cc: James Cowgill <James.Cowgill@imgtec.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Alex Smith <alex.smith@imgtec.com> Cc: Adam Buchbinder <adam.buchbinder@gmail.com> Cc: Qais Yousef <qais.yousef@imgtec.com> Cc: Jiang Liu <jiang.liu@linux.intel.com> Cc: Mikko Rapeli <mikko.rapeli@iki.fi> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Brian Norris <computersforpeace@gmail.com> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: "Luis R. Rodriguez" <mcgrof@do-not-panic.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Roland McGrath <roland@hack.frob.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Kalle Valo <kvalo@qca.qualcomm.com> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Tony Wu <tung7970@gmail.com> Cc: Huaitong Han <huaitong.han@intel.com> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Juergen Gross <jgross@suse.com> Cc: Jason Cooper <jason@lakedaemon.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrea Gelmini <andrea.gelmini@gelma.net> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Rabin Vincent <rabin@rab.in> Cc: "Maciej W. Rozycki" <macro@imgtec.com> Cc: David Daney <david.daney@cavium.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-03 20:45:50 +00:00
if (!IS_ENABLED(CONFIG_DEBUG_LOCK_ALLOC))
/* ensure ww_acquire_fini will still fail if called twice */
ctx->acquired = ~0U;
#endif
}
/**
* ww_mutex_lock - acquire the w/w mutex
* @lock: the mutex to be acquired
* @ctx: w/w acquire context, or NULL to acquire only a single lock.
*
* Lock the w/w mutex exclusively for this task.
*
* Deadlocks within a given w/w class of locks are detected and handled with the
* wait/die algorithm. If the lock isn't immediately available this function
* will either sleep until it is (wait case). Or it selects the current context
* for backing off by returning -EDEADLK (die case). Trying to acquire the
* same lock with the same context twice is also detected and signalled by
* returning -EALREADY. Returns 0 if the mutex was successfully acquired.
*
* In the die case the caller must release all currently held w/w mutexes for
* the given context and then wait for this contending lock to be available by
* calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this
* lock and proceed with trying to acquire further w/w mutexes (e.g. when
* scanning through lru lists trying to free resources).
*
* The mutex must later on be released by the same task that
* acquired it. The task may not exit without first unlocking the mutex. Also,
* kernel memory where the mutex resides must not be freed with the mutex still
* locked. The mutex must first be initialized (or statically defined) before it
* can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be
* of the same w/w lock class as was used to initialize the acquire context.
*
* A mutex acquired with this function must be released with ww_mutex_unlock.
*/
locking/ww_mutex: Turn off __must_check for now With the ww_mutex inline wrappers gone there's a lot of dormant anti-patterns emerging in an x86 allyesconfig build: kernel/locking/test-ww_mutex.c:80:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] kernel/locking/test-ww_mutex.c:55:3: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] kernel/locking/test-ww_mutex.c:134:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] kernel/locking/test-ww_mutex.c:213:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] kernel/locking/test-ww_mutex.c:177:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] kernel/locking/test-ww_mutex.c:266:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:213:19: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] lib/locking-selftest.c:211:20: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/drm_modeset_lock.c:430:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c:70:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/vgem/vgem_fence.c:193:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/i915/i915_gem_batch_pool.c:125:4: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/i915/i915_gem_execbuffer.c:1302:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/radeon/radeon_prime.c:69:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] drivers/gpu/drm/nouveau/nouveau_prime.c:70:2: warning: ignoring return value of ‘ww_mutex_lock’, declared with attribute warn_unused_result [-Wunused-result] ... but we cannot just litter the kernel build log with such warnings. These need to be fixed separately - turn off the warning for now. Cc: Nicolai Hähnle <nicolai.haehnle@amd.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-01-14 11:11:59 +00:00
extern int /* __must_check */ ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx);
/**
* ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible
* @lock: the mutex to be acquired
* @ctx: w/w acquire context
*
* Lock the w/w mutex exclusively for this task.
*
* Deadlocks within a given w/w class of locks are detected and handled with the
* wait/die algorithm. If the lock isn't immediately available this function
* will either sleep until it is (wait case). Or it selects the current context
* for backing off by returning -EDEADLK (die case). Trying to acquire the
* same lock with the same context twice is also detected and signalled by
* returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a
* signal arrives while waiting for the lock then this function returns -EINTR.
*
* In the die case the caller must release all currently held w/w mutexes for
* the given context and then wait for this contending lock to be available by
* calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to
* not acquire this lock and proceed with trying to acquire further w/w mutexes
* (e.g. when scanning through lru lists trying to free resources).
*
* The mutex must later on be released by the same task that
* acquired it. The task may not exit without first unlocking the mutex. Also,
* kernel memory where the mutex resides must not be freed with the mutex still
* locked. The mutex must first be initialized (or statically defined) before it
* can be locked. memset()-ing the mutex to 0 is not allowed. The mutex must be
* of the same w/w lock class as was used to initialize the acquire context.
*
* A mutex acquired with this function must be released with ww_mutex_unlock.
*/
extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx);
/**
* ww_mutex_lock_slow - slowpath acquiring of the w/w mutex
* @lock: the mutex to be acquired
* @ctx: w/w acquire context
*
* Acquires a w/w mutex with the given context after a die case. This function
* will sleep until the lock becomes available.
*
* The caller must have released all w/w mutexes already acquired with the
* context and then call this function on the contended lock.
*
* Afterwards the caller may continue to (re)acquire the other w/w mutexes it
* needs with ww_mutex_lock. Note that the -EALREADY return code from
* ww_mutex_lock can be used to avoid locking this contended mutex twice.
*
* It is forbidden to call this function with any other w/w mutexes associated
* with the context held. It is forbidden to call this on anything else than the
* contending mutex.
*
* Note that the slowpath lock acquiring can also be done by calling
* ww_mutex_lock directly. This function here is simply to help w/w mutex
* locking code readability by clearly denoting the slowpath.
*/
static inline void
ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
int ret;
#ifdef DEBUG_WW_MUTEXES
DEBUG_LOCKS_WARN_ON(!ctx->contending_lock);
#endif
ret = ww_mutex_lock(lock, ctx);
(void)ret;
}
/**
* ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible
* @lock: the mutex to be acquired
* @ctx: w/w acquire context
*
* Acquires a w/w mutex with the given context after a die case. This function
* will sleep until the lock becomes available and returns 0 when the lock has
* been acquired. If a signal arrives while waiting for the lock then this
* function returns -EINTR.
*
* The caller must have released all w/w mutexes already acquired with the
* context and then call this function on the contended lock.
*
* Afterwards the caller may continue to (re)acquire the other w/w mutexes it
* needs with ww_mutex_lock. Note that the -EALREADY return code from
* ww_mutex_lock can be used to avoid locking this contended mutex twice.
*
* It is forbidden to call this function with any other w/w mutexes associated
* with the given context held. It is forbidden to call this on anything else
* than the contending mutex.
*
* Note that the slowpath lock acquiring can also be done by calling
* ww_mutex_lock_interruptible directly. This function here is simply to help
* w/w mutex locking code readability by clearly denoting the slowpath.
*/
static inline int __must_check
ww_mutex_lock_slow_interruptible(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx)
{
#ifdef DEBUG_WW_MUTEXES
DEBUG_LOCKS_WARN_ON(!ctx->contending_lock);
#endif
return ww_mutex_lock_interruptible(lock, ctx);
}
extern void ww_mutex_unlock(struct ww_mutex *lock);
kernel/locking: Add context to ww_mutex_trylock() i915 will soon gain an eviction path that trylock a whole lot of locks for eviction, getting dmesg failures like below: BUG: MAX_LOCK_DEPTH too low! turning off the locking correctness validator. depth: 48 max: 48! 48 locks held by i915_selftest/5776: #0: ffff888101a79240 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x88/0x160 #1: ffffc900009778c0 (reservation_ww_class_acquire){+.+.}-{0:0}, at: i915_vma_pin.constprop.63+0x39/0x1b0 [i915] #2: ffff88800cf74de8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_vma_pin.constprop.63+0x5f/0x1b0 [i915] #3: ffff88810c7f9e38 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c4/0x9d0 [i915] #4: ffff88810bad5768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] #5: ffff88810bad60e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] ... #46: ffff88811964d768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] #47: ffff88811964e0e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] INFO: lockdep is turned off. Fixing eviction to nest into ww_class_acquire is a high priority, but it requires a rework of the entire driver, which can only be done one step at a time. As an intermediate solution, add an acquire context to ww_mutex_trylock, which allows us to do proper nesting annotations on the trylocks, making the above lockdep splat disappear. This is also useful in regulator_lock_nested, which may avoid dropping regulator_nesting_mutex in the uncontended path, so use it there. TTM may be another user for this, where we could lock a buffer in a fastpath with list locks held, without dropping all locks we hold. [peterz: rework actual ww_mutex_trylock() implementations] Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/YUBGPdDDjKlxAuXJ@hirez.programming.kicks-ass.net
2021-09-09 09:32:18 +00:00
extern int __must_check ww_mutex_trylock(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx);
/***
* ww_mutex_destroy - mark a w/w mutex unusable
* @lock: the mutex to be destroyed
*
* This function marks the mutex uninitialized, and any subsequent
* use of the mutex is forbidden. The mutex must not be locked when
* this function is called.
*/
static inline void ww_mutex_destroy(struct ww_mutex *lock)
{
#ifndef CONFIG_PREEMPT_RT
mutex_destroy(&lock->base);
#endif
}
/**
* ww_mutex_is_locked - is the w/w mutex locked
* @lock: the mutex to be queried
*
* Returns 1 if the mutex is locked, 0 if unlocked.
*/
static inline bool ww_mutex_is_locked(struct ww_mutex *lock)
{
return ww_mutex_base_is_locked(&lock->base);
}
#endif