workqueue: add CONFIG_BOOTPARAM_WQ_STALL_PANIC option

Add a kernel config option to set the default value of
workqueue.panic_on_stall, similar to CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC,
CONFIG_BOOTPARAM_HARDLOCKUP_PANIC and CONFIG_BOOTPARAM_HUNG_TASK_PANIC.

This allows setting the number of workqueue stalls before triggering
a kernel panic at build time, which is useful for high-availability
systems that need consistent panic-on-stall, in other words, those
servers which run with CONFIG_BOOTPARAM_*_PANIC=y already.

The default remains 0 (disabled). Setting it to 1 will panic on the
first stall, and higher values will panic after that many stall
warnings. The value can still be overridden at runtime via the
workqueue.panic_on_stall boot parameter or sysfs.

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a8d0afde7f85a506b827ae31d48fc5d9dbabc095..5a9df399dd72208da2cdf393047b4324cf53e998 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -8336,7 +8336,8 @@ Kernel parameters
                        CONFIG_WQ_WATCHDOG. It sets the number times of the
                        stall to trigger panic.
 
-                       The default is 0, which disables the panic on stall.
+                       The default is set by CONFIG_BOOTPARAM_WQ_STALL_PANIC,
+                       which is 0 (disabled) if not configured.
 
        workqueue.cpu_intensive_thresh_us=
                        Per-cpu work items which run for longer than this

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 64fe81f30e852aacda7acc1074223e8aba48ecdb..2e7fd46fce1703768a573351e8666172bb10f6fd 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -7568,7 +7568,7 @@ static struct timer_list wq_watchdog_timer;
 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
 
-static unsigned int wq_panic_on_stall;
+static unsigned int wq_panic_on_stall = CONFIG_BOOTPARAM_WQ_STALL_PANIC;
 module_param_named(panic_on_stall, wq_panic_on_stall, uint, 0644);
 
 /*

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ba36939fda79bf890834b586c366a28acd434ef9..ce25a8faf6e9e7ab861969f194eeca8dfe477129 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1297,6 +1297,29 @@ config WQ_WATCHDOG
          state.  This can be configured through kernel parameter
          "workqueue.watchdog_thresh" and its sysfs counterpart.
 
+config BOOTPARAM_WQ_STALL_PANIC
+       int "Panic on Nth workqueue stall"
+       default 0
+       range 0 100
+       depends on WQ_WATCHDOG
+       help
+         Set the number of workqueue stalls to trigger a kernel panic.
+         A workqueue stall occurs when a worker pool doesn't make forward
+         progress on a pending work item for over 30 seconds (configurable
+         using the workqueue.watchdog_thresh parameter).
+
+         If n = 0, the kernel will not panic on stall. If n > 0, the kernel
+         will panic after n stall warnings.
+
+         The panic can be used in combination with panic_timeout,
+         to cause the system to reboot automatically after a
+         stall has been detected. This feature is useful for
+         high-availability systems that have uptime guarantees and
+         where a stall must be resolved ASAP.
+
+         This setting can be overridden at runtime via the
+         workqueue.panic_on_stall kernel parameter.
+
 config WQ_CPU_INTENSIVE_REPORT
        bool "Report per-cpu work items which hog CPU for too long"
        depends on DEBUG_KERNEL