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sched_ext: Pass locked CPU parameter to scx_hardlockup() and add docs

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With the buddy lockup detector, smp_processor_id() returns the detecting CPU,
not the locked CPU, making scx_hardlockup()'s printouts confusing. Pass the
locked CPU number from watchdog_hardlockup_check() as a parameter instead.

Also add kerneldoc comments to handle_lockup(), scx_hardlockup(), and
scx_rcu_cpu_stall() documenting their return value semantics.

Suggested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo
2025-11-13 15:33:41 -10:00
parent 67932f6918
commit 1dcb98bbb7
3 changed files with 25 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/sched/ext.h
View File

@@ -230,7 +230,7 @@ struct sched_ext_entity {
void sched_ext_dead(struct task_struct *p);
void print_scx_info(const char *log_lvl, struct task_struct *p);
void scx_softlockup(u32 dur_s);
bool scx_hardlockup(void);
bool scx_hardlockup(int cpu);
bool scx_rcu_cpu_stall(void);
#else /* !CONFIG_SCHED_CLASS_EXT */
@@ -238,7 +238,7 @@ bool scx_rcu_cpu_stall(void);
static inline void sched_ext_dead(struct task_struct *p) {}
static inline void print_scx_info(const char *log_lvl, struct task_struct *p) {}
static inline void scx_softlockup(u32 dur_s) {}
static inline bool scx_hardlockup(void) { return false; }
static inline bool scx_hardlockup(int cpu) { return false; }
static inline bool scx_rcu_cpu_stall(void) { return false; }
#endif /* CONFIG_SCHED_CLASS_EXT */

25
kernel/sched/ext.c
View File

@@ -3687,6 +3687,17 @@ bool scx_allow_ttwu_queue(const struct task_struct *p)
return false;
}
/**
* handle_lockup - sched_ext common lockup handler
* @fmt: format string
*
* Called on system stall or lockup condition and initiates abort of sched_ext
* if enabled, which may resolve the reported lockup.
*
* Returns %true if sched_ext is enabled and abort was initiated, which may
* resolve the lockup. %false if sched_ext is not enabled or abort was already
* initiated by someone else.
*/
static __printf(1, 2) bool handle_lockup(const char *fmt, ...)
{
struct scx_sched *sch;
@@ -3718,6 +3729,10 @@ static __printf(1, 2) bool handle_lockup(const char *fmt, ...)
* that may not be caused by the current BPF scheduler, try kicking out the
* current scheduler in an attempt to recover the system to a good state before
* issuing panics.
*
* Returns %true if sched_ext is enabled and abort was initiated, which may
* resolve the reported RCU stall. %false if sched_ext is not enabled or someone
* else already initiated abort.
*/
bool scx_rcu_cpu_stall(void)
{
@@ -3750,14 +3765,18 @@ void scx_softlockup(u32 dur_s)
* numerous affinitized tasks in a single queue and directing all CPUs at it.
* Try kicking out the current scheduler in an attempt to recover the system to
* a good state before taking more drastic actions.
*
* Returns %true if sched_ext is enabled and abort was initiated, which may
* resolve the reported hardlockdup. %false if sched_ext is not enabled or
* someone else already initiated abort.
*/
bool scx_hardlockup(void)
bool scx_hardlockup(int cpu)
{
if (!handle_lockup("hard lockup - CPU %d", smp_processor_id()))
if (!handle_lockup("hard lockup - CPU %d", cpu))
return false;
printk_deferred(KERN_ERR "sched_ext: Hard lockup - CPU %d, disabling BPF scheduler\n",
smp_processor_id());
cpu);
return true;
}

2
kernel/watchdog.c
View File

@@ -203,7 +203,7 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
* only once when sched_ext is enabled and will immediately
* abort the BPF scheduler and print out a warning message.
*/
if (scx_hardlockup())
if (scx_hardlockup(cpu))
return;
/* Only print hardlockups once. */