The patch titled
Subject: watchdog/hardlockup: avoid large stack frames in watchdog_hardlockup_check()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
watchdog-hardlockup-avoid-large-stack-frames-in-watchdog_hardlockup_check.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-hardlockup-avoid-large-stack-frames-in-watchdog_hardlockup_check.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Douglas Anderson <dianders@xxxxxxxxxxxx>
Subject: watchdog/hardlockup: avoid large stack frames in watchdog_hardlockup_check()
Date: Fri, 4 Aug 2023 07:00:43 -0700
After commit 77c12fc95980 ("watchdog/hardlockup: add a "cpu" param to
watchdog_hardlockup_check()") we started storing a `struct cpumask` on the
stack in watchdog_hardlockup_check(). On systems with CONFIG_NR_CPUS set
to 8192 this takes up 1K on the stack. That triggers warnings with
`CONFIG_FRAME_WARN` set to 1024.
We'll use the new trigger_allbutcpu_cpu_backtrace() to avoid needing to
use a CPU mask at all.
Link: https://lkml.kernel.org/r/20230804065935.v4.2.I501ab68cb926ee33a7c87e063d207abf09b9943c@changeid
Fixes: 77c12fc95980 ("watchdog/hardlockup: add a "cpu" param to watchdog_hardlockup_check()")
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/r/202307310955.pLZDhpnl-lkp@xxxxxxxxx
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Pingfan Liu <kernelfans@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
--- a/kernel/watchdog.c~watchdog-hardlockup-avoid-large-stack-frames-in-watchdog_hardlockup_check
+++ a/kernel/watchdog.c
@@ -151,9 +151,6 @@ void watchdog_hardlockup_check(unsigned
*/
if (is_hardlockup(cpu)) {
unsigned int this_cpu = smp_processor_id();
- struct cpumask backtrace_mask;
-
- cpumask_copy(&backtrace_mask, cpu_online_mask);
/* Only print hardlockups once. */
if (per_cpu(watchdog_hardlockup_warned, cpu))
@@ -167,10 +164,8 @@ void watchdog_hardlockup_check(unsigned
show_regs(regs);
else
dump_stack();
- cpumask_clear_cpu(cpu, &backtrace_mask);
} else {
- if (trigger_single_cpu_backtrace(cpu))
- cpumask_clear_cpu(cpu, &backtrace_mask);
+ trigger_single_cpu_backtrace(cpu);
}
/*
@@ -179,7 +174,7 @@ void watchdog_hardlockup_check(unsigned
*/
if (sysctl_hardlockup_all_cpu_backtrace &&
!test_and_set_bit(0, &watchdog_hardlockup_all_cpu_dumped))
- trigger_cpumask_backtrace(&backtrace_mask);
+ trigger_allbutcpu_cpu_backtrace(cpu);
if (hardlockup_panic)
nmi_panic(regs, "Hard LOCKUP");
_
Patches currently in -mm which might be from dianders@xxxxxxxxxxxx are
nmi_backtrace-allow-excluding-an-arbitrary-cpu.patch
watchdog-hardlockup-avoid-large-stack-frames-in-watchdog_hardlockup_check.patch
