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workqueue: add time-based panic for stalls 

Add a new module parameter 'panic_on_stall_time' that triggers a panic
when a workqueue stall persists for longer than the specified duration
in seconds.

Unlike 'panic_on_stall' which counts accumulated stall events, this
parameter triggers based on the duration of a single continuous stall.
This is useful for catching truly stuck workqueues rather than
accumulating transient stalls.

Usage:
  workqueue.panic_on_stall_time=120

This would panic if any workqueue pool has been stalled for 120 seconds
or more.

The stall duration is measured from the workqueue last progress
(poll_ts) which accounts for legitimate system stalls.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Breno Leitao 2026-02-06 03:18:01 -08:00 committed by Tejun Heo
parent 32d572e390
commit f84c9dd34e
2 changed files with 26 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
Documentation/admin-guide/kernel-parameters.txt
View File

@ -8339,6 +8339,14 @@ Kernel parameters
The default is set by CONFIG_BOOTPARAM_WQ_STALL_PANIC,
which is 0 (disabled) if not configured.
workqueue.panic_on_stall_time=<uint>
Panic when a workqueue stall has been continuous for
the specified number of seconds. Unlike panic_on_stall
which counts accumulated stall events, this triggers
based on the duration of a single continuous stall.
The default is 0, which disables the time-based panic.
workqueue.cpu_intensive_thresh_us=
Per-cpu work items which run for longer than this
threshold are automatically considered CPU intensive

22
kernel/workqueue.c
View File

@ -7571,6 +7571,10 @@ static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
static unsigned int wq_panic_on_stall = CONFIG_BOOTPARAM_WQ_STALL_PANIC;
module_param_named(panic_on_stall, wq_panic_on_stall, uint, 0644);
static unsigned int wq_panic_on_stall_time;
module_param_named(panic_on_stall_time, wq_panic_on_stall_time, uint, 0644);
MODULE_PARM_DESC(panic_on_stall_time, "Panic if stall exceeds this many seconds (0=disabled)");
/*
* Show workers that might prevent the processing of pending work items.
* The only candidates are CPU-bound workers in the running state.
@ -7622,7 +7626,12 @@ static void show_cpu_pools_hogs(void)
rcu_read_unlock();
}
static void panic_on_wq_watchdog(void)
/*
* It triggers a panic in two scenarios: when the total number of stalls
* exceeds a threshold, and when a stall lasts longer than
* wq_panic_on_stall_time
*/
static void panic_on_wq_watchdog(unsigned int stall_time_sec)
{
static unsigned int wq_stall;
@ -7630,6 +7639,8 @@ static void panic_on_wq_watchdog(void)
wq_stall++;
BUG_ON(wq_stall >= wq_panic_on_stall);
}
BUG_ON(wq_panic_on_stall_time && stall_time_sec >= wq_panic_on_stall_time);
}
static void wq_watchdog_reset_touched(void)
@ -7644,10 +7655,12 @@ static void wq_watchdog_reset_touched(void)
static void wq_watchdog_timer_fn(struct timer_list *unused)
{
unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
unsigned int max_stall_time = 0;
bool lockup_detected = false;
bool cpu_pool_stall = false;
unsigned long now = jiffies;
struct worker_pool *pool;
unsigned int stall_time;
int pi;
if (!thresh)
@ -7681,14 +7694,15 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
/* did we stall? */
if (time_after(now, ts + thresh)) {
lockup_detected = true;
stall_time = jiffies_to_msecs(now - pool_ts) / 1000;
max_stall_time = max(max_stall_time, stall_time);
if (pool->cpu >= 0 && !(pool->flags & POOL_BH)) {
pool->cpu_stall = true;
cpu_pool_stall = true;
}
pr_emerg("BUG: workqueue lockup - pool");
pr_cont_pool_info(pool);
pr_cont(" stuck for %us!\n",
jiffies_to_msecs(now - pool_ts) / 1000);
pr_cont(" stuck for %us!\n", stall_time);
}
@ -7701,7 +7715,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
show_cpu_pools_hogs();
if (lockup_detected)
panic_on_wq_watchdog();
panic_on_wq_watchdog(max_stall_time);
wq_watchdog_reset_touched();
mod_timer(&wq_watchdog_timer, jiffies + thresh);