Repository files (latest commit first)

Filename	Latest commit message	Latest commit date
Muchun Song dfbbed769f printk: fix deadlock when kernel panic ... commit 8a8109f303e25a27f92c1d8edd67d7cbbc60a4eb upstream. printk_safe_flush_on_panic() caused the following deadlock on our server: CPU0: CPU1: panic rcu_dump_cpu_stacks kdump_nmi_shootdown_cpus nmi_trigger_cpumask_backtrace register_nmi_handler(crash_nmi_callback) printk_safe_flush __printk_safe_flush raw_spin_lock_irqsave(&read_lock) // send NMI to other processors apic_send_IPI_allbutself(NMI_VECTOR) // NMI interrupt, dead loop crash_nmi_callback printk_safe_flush_on_panic printk_safe_flush __printk_safe_flush // deadlock raw_spin_lock_irqsave(&read_lock) DEADLOCK: read_lock is taken on CPU1 and will never get released. It happens when panic() stops a CPU by NMI while it has been in the middle of printk_safe_flush(). Handle the lock the same way as logbuf_lock. The printk_safe buffers are flushed only when both locks can be safely taken. It can avoid the deadlock _in this particular case_ at expense of losing contents of printk_safe buffers. Note: It would actually be safe to re-init the locks when all CPUs were stopped by NMI. But it would require passing this information from arch-specific code. It is not worth the complexity. Especially because logbuf_lock and printk_safe buffers have been obsoleted by the lockless ring buffer. Fixes: cf9b1106c8 ("printk/nmi: flush NMI messages on the system panic") Signed-off-by: Muchun Song <songmuchun@bytedance.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: <stable@vger.kernel.org> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210210034823.64867-1-songmuchun@bytedance.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-03-04 10:26:50 +01:00
..
bpf	bpf_lru_list: Read double-checked variable once without lock	2021-03-04 10:26:16 +01:00
cgroup	cgroup: fix psi monitor for root cgroup	2021-02-17 10:35:14 +01:00
configs
debug	kdb: Make memory allocations more robust	2021-03-04 10:26:10 +01:00
dma	swiotlb: fix "x86: Don't panic if can not alloc buffer for swiotlb"	2020-11-18 19:20:32 +01:00
events	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:44:55 +01:00
gcov	gcov: add support for GCC 10.1	2020-09-17 13:47:56 +02:00
irq	genirq/msi: Activate Multi-MSI early when MSI_FLAG_ACTIVATE_EARLY is set	2021-02-10 09:25:30 +01:00
livepatch
locking	rtmutex: Remove unused argument from rt_mutex_proxy_unlock()	2021-01-30 13:54:09 +01:00
power	PM: hibernate: flush swap writer after marking	2021-02-03 23:25:57 +01:00
printk	printk: fix deadlock when kernel panic	2021-03-04 10:26:50 +01:00
rcu	rcu/nocb: Perform deferred wake up before last idle's need_resched() check	2021-03-04 10:26:47 +01:00
sched	rcu/nocb: Perform deferred wake up before last idle's need_resched() check	2021-03-04 10:26:47 +01:00
time	tick/sched: Remove bogus boot "safety" check	2021-01-06 14:48:40 +01:00
trace	tracing: Check length before giving out the filter buffer	2021-02-17 10:35:14 +01:00
.gitignore
acct.c
async.c
audit.c	audit: fix a net reference leak in audit_list_rules_send()	2020-06-22 09:30:59 +02:00
audit.h	audit: fix a net reference leak in audit_list_rules_send()	2020-06-22 09:30:59 +02:00
audit_fsnotify.c
audit_tree.c
audit_watch.c	audit: CONFIG_CHANGE don't log internal bookkeeping as an event	2020-10-01 13:17:32 +02:00
auditfilter.c	audit: fix a net reference leak in audit_list_rules_send()	2020-06-22 09:30:59 +02:00
auditsc.c
backtracetest.c
bounds.c
capability.c
compat.c
configs.c
context_tracking.c
cpu.c	kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling	2020-12-30 11:50:56 +01:00
cpu_pm.c	kernel/cpu_pm: Fix uninitted local in cpu_pm	2020-06-22 09:31:22 +02:00
crash_core.c
crash_dump.c
cred.c	keys: Fix request_key() cache	2020-01-17 19:48:42 +01:00
delayacct.c
dma.c
exec_domain.c
exit.c	don't dump the threads that had been already exiting when zapped.	2020-11-18 19:20:31 +01:00
extable.c
fail_function.c	fail_function: Remove a redundant mutex unlock	2020-11-24 13:29:18 +01:00
fork.c	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:44:55 +01:00
freezer.c	Revert "libata, freezer: avoid block device removal while system is frozen"	2019-10-06 09:11:37 -06:00
futex.c	futex: Handle faults correctly for PI futexes	2021-01-30 13:54:10 +01:00
gen_kheaders.sh	kbuild: add variables for compression tools	2020-09-03 11:27:10 +02:00
groups.c
hung_task.c
iomem.c
irq_work.c
jump_label.c
kallsyms.c	kallsyms: Refactor kallsyms_show_value() to take cred	2020-07-16 08:16:44 +02:00
kcmp.c	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:44:55 +01:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c
kexec.c
kexec_core.c	kernel: kexec: remove the lock operation of system_transition_mutex	2021-02-03 23:25:56 +01:00
kexec_elf.c
kexec_file.c	ima: Free IMA measurement buffer after kexec syscall	2021-03-04 10:26:25 +01:00
kexec_internal.h
kheaders.c
kmod.c	kmod: make request_module() return an error when autoloading is disabled	2020-04-17 10:50:22 +02:00
kprobes.c	tracing/kprobe: Fix to support kretprobe events on unloaded modules	2021-02-13 13:52:54 +01:00
ksysfs.c
kthread.c	kthread: Extract KTHREAD_IS_PER_CPU	2021-02-07 15:35:49 +01:00
latencytop.c
Makefile	elfcore: fix building with clang	2021-01-23 15:57:55 +01:00
module-internal.h
module.c	module: Ignore _GLOBAL_OFFSET_TABLE_ when warning for undefined symbols	2021-03-04 10:26:49 +01:00
module_signature.c
module_signing.c
notifier.c	kernel/notifier.c: intercept duplicate registrations to avoid infinite loops	2020-10-01 13:17:23 +02:00
nsproxy.c
padata.c	padata: add separate cpuhp node for CPUHP_PADATA_DEAD	2020-06-17 16:40:22 +02:00
panic.c	panic: ensure preemption is disabled during panic()	2019-10-07 15:47:19 -07:00
params.c
pid.c
pid_namespace.c
profile.c
ptrace.c	ptrace: Set PF_SUPERPRIV when checking capability	2020-11-24 13:29:24 +01:00
range.c
reboot.c	reboot: fix overflow parsing reboot cpu number	2020-11-18 19:20:30 +01:00
relay.c	kernel/relay.c: fix memleak on destroy relay channel	2020-08-26 10:40:51 +02:00
resource.c	/dev/mem: Revoke mappings when a driver claims the region	2020-06-24 17:50:35 +02:00
rseq.c
seccomp.c	seccomp: Add missing return in non-void function	2021-03-04 10:26:45 +01:00
signal.c	ptrace: fix task_join_group_stop() for the case when current is traced	2020-11-10 12:37:24 +01:00
smp.c
smpboot.c	kthread: Extract KTHREAD_IS_PER_CPU	2021-02-07 15:35:49 +01:00
smpboot.h
softirq.c
stackleak.c
stacktrace.c	stacktrace: Don't skip first entry on noncurrent tasks	2019-11-04 21:19:25 +01:00
stop_machine.c	stop_machine: Avoid potential race behaviour	2019-10-17 12:47:12 +02:00
sys.c	kernel/sys.c: avoid copying possible padding bytes in copy_to_user	2020-10-01 13:17:23 +02:00
sys_ni.c
sysctl-test.c	kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()	2020-10-01 13:17:10 +02:00
sysctl.c	kernel: sysctl: make drop_caches write-only	2020-01-04 19:18:32 +01:00
sysctl_binary.c
task_work.c
taskstats.c	taskstats: fix data-race	2020-01-09 10:19:54 +01:00
test_kprobes.c
torture.c
tracepoint.c	tracepoint: Do not fail unregistering a probe due to memory failure	2021-03-04 10:26:32 +01:00
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c	usermodehelper: reset umask to default before executing user process	2020-10-14 10:32:58 +02:00
up.c
user-return-notifier.c
user.c
user_namespace.c
utsname.c
utsname_sysctl.c
watchdog.c	watchdog/softlockup: Enforce that timestamp is valid on boot	2020-02-24 08:36:52 +01:00
watchdog_hld.c
workqueue.c	workqueue: Restrict affinity change to rescuer	2021-02-07 15:35:49 +01:00
workqueue_internal.h