From: Li RongQing Date: Wed, 15 Oct 2025 06:36:15 +0000 (+0800) Subject: hung_task: panic when there are more than N hung tasks at the same time X-Git-Tag: v6.19-rc1~70^2~125 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9544f9e6947f6508d29f0d0cc2dacaa749fc1613;p=thirdparty%2Fkernel%2Flinux.git hung_task: panic when there are more than N hung tasks at the same time The hung_task_panic sysctl is currently a blunt instrument: it's all or nothing. Panicking on a single hung task can be an overreaction to a transient glitch. A more reliable indicator of a systemic problem is when multiple tasks hang simultaneously. Extend hung_task_panic to accept an integer threshold, allowing the kernel to panic only when N hung tasks are detected in a single scan. This provides finer control to distinguish between isolated incidents and system-wide failures. The accepted values are: - 0: Don't panic (unchanged) - 1: Panic on the first hung task (unchanged) - N > 1: Panic after N hung tasks are detected in a single scan The original behavior is preserved for values 0 and 1, maintaining full backward compatibility. [lance.yang@linux.dev: new changelog] Link: https://lkml.kernel.org/r/20251015063615.2632-1-lirongqing@baidu.com Signed-off-by: Li RongQing Reviewed-by: Masami Hiramatsu (Google) Reviewed-by: Lance Yang Tested-by: Lance Yang Acked-by: Andrew Jeffery [aspeed_g5_defconfig] Cc: Anshuman Khandual Cc: Arnd Bergmann Cc: David Hildenbrand Cc: Florian Wesphal Cc: Jakub Kacinski Cc: Jason A. Donenfeld Cc: Joel Granados Cc: Joel Stanley Cc: Jonathan Corbet Cc: Kees Cook Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: "Paul E . McKenney" Cc: Pawan Gupta Cc: Petr Mladek Cc: Phil Auld Cc: Randy Dunlap Cc: Russell King Cc: Shuah Khan Cc: Simon Horman Cc: Stanislav Fomichev Cc: Steven Rostedt Signed-off-by: Andrew Morton --- diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6c42061ca20e5..b8f8f5d74093a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2010,14 +2010,20 @@ the added memory block itself do not be affected. hung_task_panic= - [KNL] Should the hung task detector generate panics. - Format: 0 | 1 + [KNL] Number of hung tasks to trigger kernel panic. + Format: + + When set to a non-zero value, a kernel panic will be triggered if + the number of detected hung tasks reaches this value. + + 0: don't panic + 1: panic immediately on first hung task + N: panic after N hung tasks are detected in a single scan - A value of 1 instructs the kernel to panic when a - hung task is detected. The default value is controlled - by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time - option. The value selected by this boot parameter can - be changed later by the kernel.hung_task_panic sysctl. + The default value is controlled by the + CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time option. The value + selected by this boot parameter can be changed later by the + kernel.hung_task_panic sysctl. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) terminal devices. Valid values: 0..8 diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index f3ee807b5d8b3..0065a55bc09ed 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -397,13 +397,14 @@ a hung task is detected. hung_task_panic =============== -Controls the kernel's behavior when a hung task is detected. +When set to a non-zero value, a kernel panic will be triggered if the +number of hung tasks found during a single scan reaches this value. This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. -= ================================================= += ======================================================= 0 Continue operation. This is the default behavior. -1 Panic immediately. -= ================================================= +N Panic when N hung tasks are found during a single scan. += ======================================================= hung_task_check_count diff --git a/arch/arm/configs/aspeed_g5_defconfig b/arch/arm/configs/aspeed_g5_defconfig index 61cee1e7ebea6..c3b0d5f06889f 100644 --- a/arch/arm/configs/aspeed_g5_defconfig +++ b/arch/arm/configs/aspeed_g5_defconfig @@ -308,7 +308,7 @@ CONFIG_PANIC_ON_OOPS=y CONFIG_PANIC_TIMEOUT=-1 CONFIG_SOFTLOCKUP_DETECTOR=y CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y -CONFIG_BOOTPARAM_HUNG_TASK_PANIC=y +CONFIG_BOOTPARAM_HUNG_TASK_PANIC=1 CONFIG_WQ_WATCHDOG=y # CONFIG_SCHED_DEBUG is not set CONFIG_FUNCTION_TRACER=y diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config index e81327d2cd639..9f6ab7dabf672 100644 --- a/kernel/configs/debug.config +++ b/kernel/configs/debug.config @@ -83,7 +83,7 @@ CONFIG_SLUB_DEBUG_ON=y # # Debug Oops, Lockups and Hangs # -# CONFIG_BOOTPARAM_HUNG_TASK_PANIC is not set +CONFIG_BOOTPARAM_HUNG_TASK_PANIC=0 # CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC is not set CONFIG_DEBUG_ATOMIC_SLEEP=y CONFIG_DETECT_HUNG_TASK=y diff --git a/kernel/hung_task.c b/kernel/hung_task.c index b2c1f14b8129f..84b4b049faa50 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -81,7 +81,7 @@ static unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace; * hung task is detected: */ static unsigned int __read_mostly sysctl_hung_task_panic = - IS_ENABLED(CONFIG_BOOTPARAM_HUNG_TASK_PANIC); + CONFIG_BOOTPARAM_HUNG_TASK_PANIC; static int hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) @@ -218,8 +218,11 @@ static inline void debug_show_blocker(struct task_struct *task, unsigned long ti } #endif -static void check_hung_task(struct task_struct *t, unsigned long timeout) +static void check_hung_task(struct task_struct *t, unsigned long timeout, + unsigned long prev_detect_count) { + unsigned long total_hung_task; + if (!task_is_hung(t, timeout)) return; @@ -229,9 +232,10 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) */ sysctl_hung_task_detect_count++; + total_hung_task = sysctl_hung_task_detect_count - prev_detect_count; trace_sched_process_hang(t); - if (sysctl_hung_task_panic) { + if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) { console_verbose(); hung_task_show_lock = true; hung_task_call_panic = true; @@ -300,6 +304,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) int max_count = sysctl_hung_task_check_count; unsigned long last_break = jiffies; struct task_struct *g, *t; + unsigned long prev_detect_count = sysctl_hung_task_detect_count; /* * If the system crashed already then all bets are off, @@ -320,7 +325,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) last_break = jiffies; } - check_hung_task(t, timeout); + check_hung_task(t, timeout, prev_detect_count); } unlock: rcu_read_unlock(); @@ -389,7 +394,7 @@ static const struct ctl_table hung_task_sysctls[] = { .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_ONE, + .extra2 = SYSCTL_INT_MAX, }, { .procname = "hung_task_check_count", diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index e89c024dcbdfb..19592a57e1ed9 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1257,12 +1257,13 @@ config DEFAULT_HUNG_TASK_TIMEOUT Keeping the default should be fine in most cases. config BOOTPARAM_HUNG_TASK_PANIC - bool "Panic (Reboot) On Hung Tasks" + int "Number of hung tasks to trigger kernel panic" depends on DETECT_HUNG_TASK + default 0 help - Say Y here to enable the kernel to panic on "hung tasks", - which are bugs that cause the kernel to leave a task stuck - in uninterruptible "D" state. + When set to a non-zero value, a kernel panic will be triggered + if the number of hung tasks found during a single scan reaches + this value. The panic can be used in combination with panic_timeout, to cause the system to reboot automatically after a diff --git a/tools/testing/selftests/wireguard/qemu/kernel.config b/tools/testing/selftests/wireguard/qemu/kernel.config index 936b18be07cfc..0504c11c2de62 100644 --- a/tools/testing/selftests/wireguard/qemu/kernel.config +++ b/tools/testing/selftests/wireguard/qemu/kernel.config @@ -81,7 +81,7 @@ CONFIG_WQ_WATCHDOG=y CONFIG_DETECT_HUNG_TASK=y CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y -CONFIG_BOOTPARAM_HUNG_TASK_PANIC=y +CONFIG_BOOTPARAM_HUNG_TASK_PANIC=1 CONFIG_PANIC_TIMEOUT=-1 CONFIG_STACKTRACE=y CONFIG_EARLY_PRINTK=y