[PATCH v3 2/4] watchdog: use sys_info_with_filter() to avoid duplicate backtraces
From: Bradley Morgan <hidden>
Date: 2026-06-25 15:26:26
Also in:
lkml, stable
Subsystem:
the rest · Maintainer:
Linus Torvalds
The watchdog prints all CPU backtraces itself. When the watchdog mask
contains only SYS_INFO_ALL_BT, stripping that bit leaves zero and
sys_info(0) falls back to kernel_sys_info.
Use sys_info_with_filter() so an explicit all_bt mask does not request
the global default.
Fixes: a9af76a78760 ("watchdog: add sys_info sysctls to dump sys info on system lockup")
Cc: stable@vger.kernel.org
Signed-off-by: Bradley Morgan <redacted>
---
kernel/watchdog.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 87dd5e0f6968..ff284593cb90 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c@@ -208,6 +208,7 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs) { int hardlockup_all_cpu_backtrace; unsigned int this_cpu; + unsigned long si_mask; unsigned long flags; if (per_cpu(watchdog_hardlockup_touched, cpu)) {
@@ -216,7 +217,8 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs) return; } - hardlockup_all_cpu_backtrace = (hardlockup_si_mask & SYS_INFO_ALL_BT) ? + si_mask = READ_ONCE(hardlockup_si_mask); + hardlockup_all_cpu_backtrace = (si_mask & SYS_INFO_ALL_BT) ? 1 : sysctl_hardlockup_all_cpu_backtrace; /* * Check for a hardlockup by making sure the CPU's timer
@@ -286,7 +288,7 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs) clear_bit_unlock(0, &hard_lockup_nmi_warn); } - sys_info(hardlockup_si_mask & ~SYS_INFO_ALL_BT); + sys_info_with_filter(si_mask, SYS_INFO_ALL_BT); if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP");
@@ -798,6 +800,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) struct pt_regs *regs = get_irq_regs(); int softlockup_all_cpu_backtrace; int duration, thresh_count; + unsigned long si_mask; unsigned long flags; if (!watchdog_enabled)
@@ -809,7 +812,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) if (panic_in_progress()) return HRTIMER_NORESTART; - softlockup_all_cpu_backtrace = (softlockup_si_mask & SYS_INFO_ALL_BT) ? + si_mask = READ_ONCE(softlockup_si_mask); + softlockup_all_cpu_backtrace = (si_mask & SYS_INFO_ALL_BT) ? 1 : sysctl_softlockup_all_cpu_backtrace; watchdog_hardlockup_kick();
@@ -900,7 +904,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) } add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK); - sys_info(softlockup_si_mask & ~SYS_INFO_ALL_BT); + sys_info_with_filter(si_mask, SYS_INFO_ALL_BT); thresh_count = duration / get_softlockup_thresh(); if (softlockup_panic && thresh_count >= softlockup_panic)
--
2.53.0