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Mark Salter de16dfcc51 irqchip/gic-v3: Change pr_debug message to pr_devel [ Upstream commit `b6dd4d83dc` ] The pr_debug() in gic-v3 gic_send_sgi() can trigger a circular locking warning: GICv3: CPU10: ICC_SGI1R_EL1 `5000400` ====================================================== WARNING: possible circular locking dependency detected 4.15.0+ #1 Tainted: G W ------------------------------------------------------ dynamic_debug01/1873 is trying to acquire lock: ((console_sem).lock){-...}, at: [<0000000099c891ec>] down_trylock+0x20/0x4c but task is already holding lock: (&rq->lock){-.-.}, at: [<00000000842e1587>] __task_rq_lock+0x54/0xdc which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&rq->lock){-.-.}: __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock+0x4c/0x60 task_fork_fair+0x3c/0x148 sched_fork+0x10c/0x214 copy_process.isra.32.part.33+0x4e8/0x14f0 _do_fork+0xe8/0x78c kernel_thread+0x48/0x54 rest_init+0x34/0x2a4 start_kernel+0x45c/0x488 -> #1 (&p->pi_lock){-.-.}: __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock_irqsave+0x58/0x70 try_to_wake_up+0x48/0x600 wake_up_process+0x28/0x34 __up.isra.0+0x60/0x6c up+0x60/0x68 __up_console_sem+0x4c/0x7c console_unlock+0x328/0x634 vprintk_emit+0x25c/0x390 dev_vprintk_emit+0xc4/0x1fc dev_printk_emit+0x88/0xa8 __dev_printk+0x58/0x9c _dev_info+0x84/0xa8 usb_new_device+0x100/0x474 hub_port_connect+0x280/0x92c hub_event+0x740/0xa84 process_one_work+0x240/0x70c worker_thread+0x60/0x400 kthread+0x110/0x13c ret_from_fork+0x10/0x18 -> #0 ((console_sem).lock){-...}: validate_chain.isra.34+0x6e4/0xa20 __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock_irqsave+0x58/0x70 down_trylock+0x20/0x4c __down_trylock_console_sem+0x3c/0x9c console_trylock+0x20/0xb0 vprintk_emit+0x254/0x390 vprintk_default+0x58/0x90 vprintk_func+0xbc/0x164 printk+0x80/0xa0 __dynamic_pr_debug+0x84/0xac gic_raise_softirq+0x184/0x18c smp_cross_call+0xac/0x218 smp_send_reschedule+0x3c/0x48 resched_curr+0x60/0x9c check_preempt_curr+0x70/0xdc wake_up_new_task+0x310/0x470 _do_fork+0x188/0x78c SyS_clone+0x44/0x50 __sys_trace_return+0x0/0x4 other info that might help us debug this: Chain exists of: (console_sem).lock --> &p->pi_lock --> &rq->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&rq->lock); lock(&p->pi_lock); lock(&rq->lock); lock((console_sem).lock); * DEADLOCK * 2 locks held by dynamic_debug01/1873: #0: (&p->pi_lock){-.-.}, at: [<000000001366df53>] wake_up_new_task+0x40/0x470 #1: (&rq->lock){-.-.}, at: [<00000000842e1587>] __task_rq_lock+0x54/0xdc stack backtrace: CPU: 10 PID: 1873 Comm: dynamic_debug01 Tainted: G W 4.15.0+ #1 Hardware name: GIGABYTE R120-T34-00/MT30-GS2-00, BIOS T48 10/02/2017 Call trace: dump_backtrace+0x0/0x188 show_stack+0x24/0x2c dump_stack+0xa4/0xe0 print_circular_bug.isra.31+0x29c/0x2b8 check_prev_add.constprop.39+0x6c8/0x6dc validate_chain.isra.34+0x6e4/0xa20 __lock_acquire+0x3b4/0x6e0 lock_acquire+0xf4/0x2a8 _raw_spin_lock_irqsave+0x58/0x70 down_trylock+0x20/0x4c __down_trylock_console_sem+0x3c/0x9c console_trylock+0x20/0xb0 vprintk_emit+0x254/0x390 vprintk_default+0x58/0x90 vprintk_func+0xbc/0x164 printk+0x80/0xa0 __dynamic_pr_debug+0x84/0xac gic_raise_softirq+0x184/0x18c smp_cross_call+0xac/0x218 smp_send_reschedule+0x3c/0x48 resched_curr+0x60/0x9c check_preempt_curr+0x70/0xdc wake_up_new_task+0x310/0x470 _do_fork+0x188/0x78c SyS_clone+0x44/0x50 __sys_trace_return+0x0/0x4 GICv3: CPU0: ICC_SGI1R_EL1 12000 This could be fixed with printk_deferred() but that might lessen its usefulness for debugging. So change it to pr_devel to keep it out of production kernels. Developers working on gic-v3 can enable it as needed in their kernels. Signed-off-by: Mark Salter <msalter@redhat.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2018-04-26 11:02:21 +02:00
arch	powerpc/powernv: IMC fix out of bounds memory access at shutdown	2018-04-26 11:02:20 +02:00
block	blk-mq: fix discard merge with scheduler attached	2018-04-26 11:02:15 +02:00
certs	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
crypto	crypto: aes-generic - build with -Os on gcc-7+	2018-04-12 12:32:20 +02:00
Documentation	dm thin: fix documentation relative to low water mark threshold	2018-04-26 11:02:07 +02:00
drivers	irqchip/gic-v3: Change pr_debug message to pr_devel	2018-04-26 11:02:21 +02:00
firmware	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
fs	vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when dumping vsyscall user page	2018-04-26 11:02:20 +02:00
include	cpumask: Make for_each_cpu_wrap() available on UP as well	2018-04-26 11:02:21 +02:00
init	kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK	2018-02-22 15:42:23 +01:00
ipc	ipc/shm: fix use-after-free of shm file via remap_file_pages()	2018-04-24 09:36:23 +02:00
kernel	locking/qspinlock: Ensure node->count is updated before initialising node	2018-04-26 11:02:20 +02:00
lib	bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y	2018-04-26 11:02:16 +02:00
mm	mm/fadvise: discard partial page if endbyte is also EOF	2018-04-26 11:02:15 +02:00
net	SUNRPC: Don't call __UDPX_INC_STATS() from a preemptible context	2018-04-26 11:02:19 +02:00
samples	samples/bpf: Partially fixes the bpf.o build	2018-04-26 11:02:12 +02:00
scripts	kconfig: Fix expr_free() E_NOT leak	2018-04-26 11:02:08 +02:00
security	apparmor: fix resource audit messages when auditing peer	2018-04-19 08:56:18 +02:00
sound	ASoC: rockchip: Use dummy_dai for rt5514 dsp dailink	2018-04-26 11:02:11 +02:00
tools	perf test: Fix test trace+probe_libc_inet_pton.sh for s390x	2018-04-26 11:02:20 +02:00
usr	initramfs: fix initramfs rebuilds w/ compression after disabling	2017-11-03 07:39:19 -07:00
virt	kvm: Map PFN-type memory regions as writable (if possible)	2018-04-26 11:02:13 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	kbuild: rpm-pkg: keep spec file until make mrproper	2018-02-13 10:19:46 +01:00
.mailmap	.mailmap: Add Maciej W. Rozycki's Imagination e-mail address	2017-11-10 12:16:15 -08:00
COPYING
CREDITS	MAINTAINERS: update TPM driver infrastructure changes	2017-11-09 17:58:40 -08:00
Kbuild	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
Kconfig	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
MAINTAINERS	dt-bindings: Document mti,mips-cpc binding	2018-03-15 10:54:35 +01:00
Makefile	Linux 4.14.36	2018-04-24 09:36:40 +02:00
README	README: add a new README file, pointing to the Documentation/	2016-10-24 08:12:35 -02:00

README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.