Commit b5bc0435 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Add scx_dump_lock and dump_disabled 



Add a dedicated scx_dump_lock and per-sched dump_disabled flag so that
debug dumping can be safely disabled during sched teardown without
relying on scx_sched_lock. This is a prep for the next patch which
decouples the sysrq dump path from scx_sched_lock to resolve a lock
ordering issue.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
parent 7e92cf43

kernel/sched/ext.c

+22 −3
Original line number Diff line number Diff line
@@ -136,6 +136,8 @@ static DEFINE_RAW_SPINLOCK(scx_exit_bstr_buf_lock); 
static struct scx_bstr_buf scx_exit_bstr_buf;



/* ops debug dump */

static DEFINE_RAW_SPINLOCK(scx_dump_lock);



struct scx_dump_data {

	s32			cpu;

	bool			first;
@@ -5279,6 +5281,17 @@ static void scx_unlink_sched(struct scx_sched *sch) 
	refresh_watchdog();

}



/*

 * Called to disable future dumps and wait for in-progress one while disabling

 * @sch. Once @sch becomes empty during disable, there's no point in dumping it.

 * This prevents calling dump ops on a dead sch.

 */

static void scx_disable_dump(struct scx_sched *sch)

{

	guard(raw_spinlock_irqsave)(&scx_dump_lock);

	sch->dump_disabled = true;

}



#ifdef CONFIG_EXT_SUB_SCHED

static DECLARE_WAIT_QUEUE_HEAD(scx_unlink_waitq);
@@ -5414,6 +5427,8 @@ static void scx_sub_disable(struct scx_sched *sch) 
	}

	scx_task_iter_stop(&sti);



	scx_disable_dump(sch);



	scx_cgroup_unlock();

	percpu_up_write(&scx_fork_rwsem);
@@ -5525,6 +5540,8 @@ static void scx_root_disable(struct scx_sched *sch) 
	}

	scx_task_iter_stop(&sti);



	scx_disable_dump(sch);



	scx_cgroup_lock();

	set_cgroup_sched(sch_cgroup(sch), NULL);

	scx_cgroup_unlock();
@@ -5680,7 +5697,7 @@ static __printf(2, 3) void dump_line(struct seq_buf *s, const char *fmt, ...) 


#ifdef CONFIG_TRACEPOINTS

	if (trace_sched_ext_dump_enabled()) {

		/* protected by scx_dump_state()::dump_lock */

		/* protected by scx_dump_lock */

		static char line_buf[SCX_EXIT_MSG_LEN];



		va_start(args, fmt);
@@ -5842,7 +5859,6 @@ static void scx_dump_task(struct scx_sched *sch, 
static void scx_dump_state(struct scx_sched *sch, struct scx_exit_info *ei,

			   size_t dump_len, bool dump_all_tasks)

{

	static DEFINE_RAW_SPINLOCK(dump_lock);

	static const char trunc_marker[] = "\n\n~~~~ TRUNCATED ~~~~\n";

	struct scx_dump_ctx dctx = {

		.kind = ei->kind,
@@ -5856,7 +5872,10 @@ static void scx_dump_state(struct scx_sched *sch, struct scx_exit_info *ei, 
	char *buf;

	int cpu;



	guard(raw_spinlock_irqsave)(&dump_lock);

	guard(raw_spinlock_irqsave)(&scx_dump_lock);



	if (sch->dump_disabled)

		return;



	seq_buf_init(&s, ei->dump, dump_len);

kernel/sched/ext_internal.h

+1 −0
Original line number Diff line number Diff line
@@ -1003,6 +1003,7 @@ struct scx_sched { 
	atomic_t		bypass_dsp_enable_depth;



	bool			aborting;

	bool			dump_disabled;	/* protected by scx_dump_lock */

	u32			dsp_max_batch;

	s32			level;