watchdog: softlockup: panic when lockup duration exceeds N thresholds

The softlockup_panic sysctl is currently a binary option: panic
immediately or never panic on soft lockups.

Panicking on any soft lockup, regardless of duration, can be overly
aggressive for brief stalls that may be caused by legitimate operations. 
Conversely, never panicking may allow severe system hangs to persist
undetected.

Extend softlockup_panic to accept an integer threshold, allowing the
kernel to panic only when the normalized lockup duration exceeds N
watchdog threshold periods.  This provides finer-grained control to
distinguish between transient delays and persistent system failures.

The accepted values are:
- 0: Don't panic (unchanged)
- 1: Panic when duration >= 1 * threshold (20s default, original behavior)
- N > 1: Panic when duration >= N * threshold (e.g., 2 = 40s, 3 = 60s.)

The original behavior is preserved for values 0 and 1, maintaining full
backward compatibility while allowing systems to tolerate brief lockups
while still catching severe, persistent hangs.

[lirongqing@baidu.com: v2]
  Link: https://lkml.kernel.org/r/20251218074300.4080-1-lirongqing@baidu.com
Link: https://lkml.kernel.org/r/20251216074521.2796-1-lirongqing@baidu.com
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Song Liu <song@kernel.org>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

13 files changed, 28 insertions, 25 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1058f2a6d6a8..73d846211144 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6969,12 +6969,12 @@ Kernel parameters
 
 	softlockup_panic=
 			[KNL] Should the soft-lockup detector generate panics.
-			Format: 0 | 1
+			Format: <int>
 
-			A value of 1 instructs the soft-lockup detector
-			to panic the machine when a soft-lockup occurs. It is
-			also controlled by the kernel.softlockup_panic sysctl
-			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
+			A value of non-zero instructs the soft-lockup detector
+			to panic the machine when a soft-lockup duration exceeds
+			N thresholds. It is also controlled by the kernel.softlockup_panic
+			sysctl and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
 			respective build-time switch to that functionality.
 
 	softlockup_all_cpu_backtrace=
diff --git a/arch/arm/configs/aspeed_g5_defconfig b/arch/arm/configs/aspeed_g5_defconfig
index 2e6ea13c1e9b..ec558e57d081 100644
--- a/arch/arm/configs/aspeed_g5_defconfig
+++ b/arch/arm/configs/aspeed_g5_defconfig
@@ -306,7 +306,7 @@ CONFIG_SCHED_STACK_END_CHECK=y
 CONFIG_PANIC_ON_OOPS=y
 CONFIG_PANIC_TIMEOUT=-1
 CONFIG_SOFTLOCKUP_DETECTOR=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 CONFIG_BOOTPARAM_HUNG_TASK_PANIC=1
 CONFIG_WQ_WATCHDOG=y
 # CONFIG_SCHED_DEBUG is not set
diff --git a/arch/arm/configs/pxa3xx_defconfig b/arch/arm/configs/pxa3xx_defconfig
index 07d422f0ff34..fb272e3a2337 100644
--- a/arch/arm/configs/pxa3xx_defconfig
+++ b/arch/arm/configs/pxa3xx_defconfig
@@ -100,7 +100,7 @@ CONFIG_PRINTK_TIME=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_MAGIC_SYSRQ=y
 CONFIG_DEBUG_SHIRQ=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 # CONFIG_SCHED_DEBUG is not set
 CONFIG_DEBUG_SPINLOCK=y
 CONFIG_DEBUG_SPINLOCK_SLEEP=y
diff --git a/arch/openrisc/configs/or1klitex_defconfig b/arch/openrisc/configs/or1klitex_defconfig
index fb1eb9a68bd6..984b0e3b2768 100644
--- a/arch/openrisc/configs/or1klitex_defconfig
+++ b/arch/openrisc/configs/or1klitex_defconfig
@@ -52,5 +52,5 @@ CONFIG_LSM="lockdown,yama,loadpin,safesetid,integrity,bpf"
 CONFIG_PRINTK_TIME=y
 CONFIG_PANIC_ON_OOPS=y
 CONFIG_SOFTLOCKUP_DETECTOR=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 CONFIG_BUG_ON_DATA_CORRUPTION=y
diff --git a/arch/powerpc/configs/skiroot_defconfig b/arch/powerpc/configs/skiroot_defconfig
index 2b71a6dc399e..a4114fca5a39 100644
--- a/arch/powerpc/configs/skiroot_defconfig
+++ b/arch/powerpc/configs/skiroot_defconfig
@@ -289,7 +289,7 @@ CONFIG_SCHED_STACK_END_CHECK=y
 CONFIG_DEBUG_STACKOVERFLOW=y
 CONFIG_PANIC_ON_OOPS=y
 CONFIG_SOFTLOCKUP_DETECTOR=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 CONFIG_HARDLOCKUP_DETECTOR=y
 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
 CONFIG_WQ_WATCHDOG=y
diff --git a/drivers/gpu/drm/ci/arm.config b/drivers/gpu/drm/ci/arm.config
index 411e814819a8..d7c51670da2f 100644
--- a/drivers/gpu/drm/ci/arm.config
+++ b/drivers/gpu/drm/ci/arm.config
@@ -52,7 +52,7 @@ CONFIG_TMPFS=y
 CONFIG_PROVE_LOCKING=n
 CONFIG_DEBUG_LOCKDEP=n
 CONFIG_SOFTLOCKUP_DETECTOR=n
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=n
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=0
 
 CONFIG_FW_LOADER_COMPRESS=y
 
diff --git a/drivers/gpu/drm/ci/arm64.config b/drivers/gpu/drm/ci/arm64.config
index fddfbd4d2493..ea0e30737c4d 100644
--- a/drivers/gpu/drm/ci/arm64.config
+++ b/drivers/gpu/drm/ci/arm64.config
@@ -161,7 +161,7 @@ CONFIG_TMPFS=y
 CONFIG_PROVE_LOCKING=n
 CONFIG_DEBUG_LOCKDEP=n
 CONFIG_SOFTLOCKUP_DETECTOR=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 
 CONFIG_DETECT_HUNG_TASK=y
 
diff --git a/drivers/gpu/drm/ci/x86_64.config b/drivers/gpu/drm/ci/x86_64.config
index 8eaba388b141..7ac98a78691e 100644
--- a/drivers/gpu/drm/ci/x86_64.config
+++ b/drivers/gpu/drm/ci/x86_64.config
@@ -47,7 +47,7 @@ CONFIG_TMPFS=y
 CONFIG_PROVE_LOCKING=n
 CONFIG_DEBUG_LOCKDEP=n
 CONFIG_SOFTLOCKUP_DETECTOR=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 
 CONFIG_DETECT_HUNG_TASK=y
 
diff --git a/kernel/configs/debug.config b/kernel/configs/debug.config
index 9f6ab7dabf67..774702591d26 100644
--- a/kernel/configs/debug.config
+++ b/kernel/configs/debug.config
@@ -84,7 +84,7 @@ CONFIG_SLUB_DEBUG_ON=y
 # Debug Oops, Lockups and Hangs
 #
 CONFIG_BOOTPARAM_HUNG_TASK_PANIC=0
-# CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC is not set
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=0
 CONFIG_DEBUG_ATOMIC_SLEEP=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_PANIC_ON_OOPS=y
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 366122f4a0f8..b4d5fbdb933a 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -363,7 +363,7 @@ static struct cpumask watchdog_allowed_mask __read_mostly;
 
 /* Global variables, exported for sysctl */
 unsigned int __read_mostly softlockup_panic =
-			IS_ENABLED(CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC);
+			CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC;
 
 static bool softlockup_initialized __read_mostly;
 static u64 __read_mostly sample_period;
@@ -774,8 +774,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 {
 	unsigned long touch_ts, period_ts, now;
 	struct pt_regs *regs = get_irq_regs();
-	int duration;
 	int softlockup_all_cpu_backtrace;
+	int duration, thresh_count;
 	unsigned long flags;
 
 	if (!watchdog_enabled)
@@ -879,7 +879,9 @@ 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);
-		if (softlockup_panic)
+		thresh_count = duration / get_softlockup_thresh();
+
+		if (softlockup_panic && thresh_count >= softlockup_panic)
 			panic("softlockup: hung tasks");
 	}
 
@@ -1228,7 +1230,7 @@ static const struct ctl_table watchdog_sysctls[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
+		.extra2		= SYSCTL_INT_MAX,
 	},
 	{
 		.procname	= "softlockup_sys_info",
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 4bfca37f313e..947e62e92da8 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1110,13 +1110,14 @@ config SOFTLOCKUP_DETECTOR_INTR_STORM
 	  the CPU stats and the interrupt counts during the "soft lockups".
 
 config BOOTPARAM_SOFTLOCKUP_PANIC
-	bool "Panic (Reboot) On Soft Lockups"
+	int "Panic (Reboot) On Soft Lockups"
 	depends on SOFTLOCKUP_DETECTOR
+	default 0
 	help
-	  Say Y here to enable the kernel to panic on "soft lockups",
-	  which are bugs that cause the kernel to loop in kernel
-	  mode for more than 20 seconds (configurable using the watchdog_thresh
-	  sysctl), without giving other tasks a chance to run.
+	  Set to a non-zero value N to enable the kernel to panic on "soft
+	  lockups", which are bugs that cause the kernel to loop in kernel
+	  mode for more than (N * 20 seconds) (configurable using the
+	  watchdog_thresh sysctl), without giving other tasks a chance to run.
 
 	  The panic can be used in combination with panic_timeout,
 	  to cause the system to reboot automatically after a
@@ -1124,7 +1125,7 @@ config BOOTPARAM_SOFTLOCKUP_PANIC
 	  high-availability systems that have uptime guarantees and
 	  where a lockup must be resolved ASAP.
 
-	  Say N if unsure.
+	  Say 0 if unsure.
 
 config HAVE_HARDLOCKUP_DETECTOR_BUDDY
 	bool
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 558839e3c185..24855381290d 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -1,6 +1,6 @@
 CONFIG_BLK_DEV_LOOP=y
 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 CONFIG_BPF=y
 CONFIG_BPF_EVENTS=y
 CONFIG_BPF_JIT=y
diff --git a/tools/testing/selftests/wireguard/qemu/kernel.config b/tools/testing/selftests/wireguard/qemu/kernel.config
index 0504c11c2de6..bb89d2dfaa2a 100644
--- a/tools/testing/selftests/wireguard/qemu/kernel.config
+++ b/tools/testing/selftests/wireguard/qemu/kernel.config
@@ -80,7 +80,7 @@ CONFIG_HARDLOCKUP_DETECTOR=y
 CONFIG_WQ_WATCHDOG=y
 CONFIG_DETECT_HUNG_TASK=y
 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC=y
-CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
+CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=1
 CONFIG_BOOTPARAM_HUNG_TASK_PANIC=1
 CONFIG_PANIC_TIMEOUT=-1
 CONFIG_STACKTRACE=y