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watchdog/hardlockup: make HAVE_NMI_WATCHDOG sparc64-specific 

There are several hardlockup detector implementations and several Kconfig
values which allow selection and build of the preferred one.

CONFIG_HARDLOCKUP_DETECTOR was introduced by the commit 23637d477c
("lockup_detector: Introduce CONFIG_HARDLOCKUP_DETECTOR") in v2.6.36.
It was a preparation step for introducing the new generic perf hardlockup
detector.

The existing arch-specific variants did not support the to-be-created
generic build configurations, sysctl interface, etc. This distinction
was made explicit by the commit 4a7863cc2e ("x86, nmi_watchdog:
Remove ARCH_HAS_NMI_WATCHDOG and rely on CONFIG_HARDLOCKUP_DETECTOR")
in v2.6.38.

CONFIG_HAVE_NMI_WATCHDOG was introduced by the commit d314d74c69
("nmi watchdog: do not use cpp symbol in Kconfig") in v3.4-rc1. It replaced
the above mentioned ARCH_HAS_NMI_WATCHDOG. At that time, it was still used
by three architectures, namely blackfin, mn10300, and sparc.

The support for blackfin and mn10300 architectures has been completely
dropped some time ago. And sparc is the only architecture with the historic
NMI watchdog at the moment.

And the old sparc implementation is really special. It is always built on
sparc64. It used to be always enabled until the commit 7a5c8b57ce
("sparc: implement watchdog_nmi_enable and watchdog_nmi_disable") added
in v4.10-rc1.

There are only few locations where the sparc64 NMI watchdog interacts
with the generic hardlockup detectors code:

  + implements arch_touch_nmi_watchdog() which is called from the generic
    touch_nmi_watchdog()

  + implements watchdog_hardlockup_enable()/disable() to support
    /proc/sys/kernel/nmi_watchdog

  + is always preferred over other generic watchdogs, see
    CONFIG_HARDLOCKUP_DETECTOR

  + includes asm/nmi.h into linux/nmi.h because some sparc-specific
    functions are needed in sparc-specific code which includes
    only linux/nmi.h.

The situation became more complicated after the commit 05a4a95279
("kernel/watchdog: split up config options") and commit 2104180a53
("powerpc/64s: implement arch-specific hardlockup watchdog") in v4.13-rc1.
They introduced HAVE_HARDLOCKUP_DETECTOR_ARCH. It was used for powerpc
specific hardlockup detector. It was compatible with the perf one
regarding the general boot, sysctl, and programming interfaces.

HAVE_HARDLOCKUP_DETECTOR_ARCH was defined as a superset of
HAVE_NMI_WATCHDOG. It made some sense because all arch-specific
detectors had some common requirements, namely:

  + implemented arch_touch_nmi_watchdog()
  + included asm/nmi.h into linux/nmi.h
  + defined the default value for /proc/sys/kernel/nmi_watchdog

But it actually has made things pretty complicated when the generic
buddy hardlockup detector was added. Before the generic perf detector
was newer supported together with an arch-specific one. But the buddy
detector could work on any SMP system. It means that an architecture
could support both the arch-specific and buddy detector.

As a result, there are few tricky dependencies. For example,
CONFIG_HARDLOCKUP_DETECTOR depends on:

  ((HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_BUDDY) && !HAVE_NMI_WATCHDOG) || HAVE_HARDLOCKUP_DETECTOR_ARCH

The problem is that the very special sparc implementation is defined as:

  HAVE_NMI_WATCHDOG && !HAVE_HARDLOCKUP_DETECTOR_ARCH

Another problem is that the meaning of HAVE_NMI_WATCHDOG is far from clear
without reading understanding the history.

Make the logic less tricky and more self-explanatory by making
HAVE_NMI_WATCHDOG specific for the sparc64 implementation. And rename it to
HAVE_HARDLOCKUP_DETECTOR_SPARC64.

Note that HARDLOCKUP_DETECTOR_PREFER_BUDDY, HARDLOCKUP_DETECTOR_PERF,
and HARDLOCKUP_DETECTOR_BUDDY may conflict only with
HAVE_HARDLOCKUP_DETECTOR_ARCH. They depend on HARDLOCKUP_DETECTOR
and it is not longer enabled when HAVE_NMI_WATCHDOG is set.

Link: https://lkml.kernel.org/r/20230616150618.6073-5-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Petr Mladek 2023-06-16 17:06:16 +02:00 committed by Andrew Morton
parent 0c68bda696
commit a5fcc2367e
6 changed files with 18 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
arch/Kconfig
View File

@ -400,23 +400,8 @@ config HAVE_HARDLOCKUP_DETECTOR_PERF
The arch chooses to use the generic perf-NMI-based hardlockup
detector. Must define HAVE_PERF_EVENTS_NMI.
config HAVE_NMI_WATCHDOG
depends on HAVE_NMI
bool
help
The arch provides its own hardlockup detector implementation instead
of the generic ones.
Sparc64 defines this variable without HAVE_HARDLOCKUP_DETECTOR_ARCH.
It is the last arch-specific implementation which was developed before
adding the common infrastructure for handling hardlockup detectors.
It is always built. It does _not_ use the common command line
parameters and sysctl interface, except for
/proc/sys/kernel/nmi_watchdog.
config HAVE_HARDLOCKUP_DETECTOR_ARCH
bool
select HAVE_NMI_WATCHDOG
help
The arch provides its own hardlockup detector implementation instead
of the generic ones.
@ -424,9 +409,6 @@ config HAVE_HARDLOCKUP_DETECTOR_ARCH
It uses the same command line parameters, and sysctl interface,
as the generic hardlockup detectors.
HAVE_NMI_WATCHDOG is selected to build the code shared with
the sparc64 specific implementation.
config HAVE_PERF_REGS
bool
help

2
arch/sparc/Kconfig
View File

@ -33,7 +33,7 @@ config SPARC
select ARCH_WANT_IPC_PARSE_VERSION
select GENERIC_PCI_IOMAP
select HAS_IOPORT
select HAVE_NMI_WATCHDOG if SPARC64
select HAVE_HARDLOCKUP_DETECTOR_SPARC64 if SPARC64
select HAVE_CBPF_JIT if SPARC32
select HAVE_EBPF_JIT if SPARC64
select HAVE_DEBUG_BUGVERBOSE

9
arch/sparc/Kconfig.debug
View File

@ -14,3 +14,12 @@ config FRAME_POINTER
bool
depends on MCOUNT
default y
config HAVE_HARDLOCKUP_DETECTOR_SPARC64
depends on HAVE_NMI
bool
help
Sparc64 hardlockup detector is the last one developed before adding
the common infrastructure for handling hardlockup detectors. It is
always built. It does _not_ use the common command line parameters
and sysctl interface, except for /proc/sys/kernel/nmi_watchdog.

5
include/linux/nmi.h
View File

@ -9,7 +9,7 @@
#include <asm/irq.h>
/* Arch specific watchdogs might need to share extra watchdog-related APIs. */
#if defined(CONFIG_HAVE_NMI_WATCHDOG)
#if defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH) || defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_SPARC64)
#include <asm/nmi.h>
#endif
@ -90,8 +90,7 @@ static inline void hardlockup_detector_disable(void) {}
#endif
/* Sparc64 has special implemetantion that is always enabled. */
#if defined(CONFIG_HARDLOCKUP_DETECTOR) || \
(defined(CONFIG_HAVE_NMI_WATCHDOG) && !defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH))
#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_SPARC64)
void arch_touch_nmi_watchdog(void);
#else
static inline void arch_touch_nmi_watchdog(void) { }

2
kernel/watchdog.c
View File

@ -29,7 +29,7 @@
static DEFINE_MUTEX(watchdog_mutex);
#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_SPARC64)
# define WATCHDOG_HARDLOCKUP_DEFAULT 1
#else
# define WATCHDOG_HARDLOCKUP_DEFAULT 0

15
lib/Kconfig.debug
View File

@ -1050,15 +1050,10 @@ config HAVE_HARDLOCKUP_DETECTOR_BUDDY
# sparc64: has a custom implementation which is not using the common
# hardlockup command line options and sysctl interface.
#
# Note that HAVE_NMI_WATCHDOG is used to distinguish the sparc64 specific
# implementaion. It is automatically enabled also for other arch-specific
# variants which set HAVE_HARDLOCKUP_DETECTOR_ARCH. It makes the check
# of avaialable and supported variants quite tricky.
#
config HARDLOCKUP_DETECTOR
bool "Detect Hard Lockups"
depends on DEBUG_KERNEL && !S390
depends on ((HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_BUDDY) && !HAVE_NMI_WATCHDOG) || HAVE_HARDLOCKUP_DETECTOR_ARCH
depends on DEBUG_KERNEL && !S390 && !HAVE_HARDLOCKUP_DETECTOR_SPARC64
depends on HAVE_HARDLOCKUP_DETECTOR_PERF || HAVE_HARDLOCKUP_DETECTOR_BUDDY || HAVE_HARDLOCKUP_DETECTOR_ARCH
imply HARDLOCKUP_DETECTOR_PERF
imply HARDLOCKUP_DETECTOR_BUDDY
select LOCKUP_DETECTOR
@ -1079,7 +1074,7 @@ config HARDLOCKUP_DETECTOR_PREFER_BUDDY
bool "Prefer the buddy CPU hardlockup detector"
depends on HARDLOCKUP_DETECTOR
depends on HAVE_HARDLOCKUP_DETECTOR_PERF && HAVE_HARDLOCKUP_DETECTOR_BUDDY
depends on !HAVE_NMI_WATCHDOG
depends on !HAVE_HARLOCKUP_DETECTOR_ARCH
help
Say Y here to prefer the buddy hardlockup detector over the perf one.
@ -1095,7 +1090,7 @@ config HARDLOCKUP_DETECTOR_PERF
bool
depends on HARDLOCKUP_DETECTOR
depends on HAVE_HARDLOCKUP_DETECTOR_PERF && !HARDLOCKUP_DETECTOR_PREFER_BUDDY
depends on !HAVE_NMI_WATCHDOG
depends on !HAVE_HARDLOCKUP_DETECTOR_ARCH
select HARDLOCKUP_DETECTOR_COUNTS_HRTIMER
config HARDLOCKUP_DETECTOR_BUDDY
@ -1103,7 +1098,7 @@ config HARDLOCKUP_DETECTOR_BUDDY
depends on HARDLOCKUP_DETECTOR
depends on HAVE_HARDLOCKUP_DETECTOR_BUDDY
depends on !HAVE_HARDLOCKUP_DETECTOR_PERF || HARDLOCKUP_DETECTOR_PREFER_BUDDY
depends on !HAVE_NMI_WATCHDOG
depends on !HAVE_HARDLOCKUP_DETECTOR_ARCH
select HARDLOCKUP_DETECTOR_COUNTS_HRTIMER
#