Commit 4ba54a6c authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Refactor lockup handlers into handle_lockup() 



scx_rcu_cpu_stall() and scx_softlockup() share the same pattern: check if the
scheduler is enabled under RCU read lock and trigger an error if so. Extract
the common pattern into handle_lockup() helper. Add scx_verror() macro and use
guard(rcu)().

This simplifies both handlers, reduces code duplication, and prepares for
hardlockup handling.

Reviewed-by: default avatarDan Schatzberg <schatzberg.dan@gmail.com>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
Cc: Emil Tsalapatis <etsal@meta.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent f2fe382e

kernel/sched/ext.c

+25 −40
Original line number Diff line number Diff line
@@ -192,6 +192,7 @@ static __printf(4, 5) bool scx_exit(struct scx_sched *sch, 
}



#define scx_error(sch, fmt, args...)	scx_exit((sch), SCX_EXIT_ERROR, 0, fmt, ##args)

#define scx_verror(sch, fmt, args)	scx_vexit((sch), SCX_EXIT_ERROR, 0, fmt, args)



#define SCX_HAS_OP(sch, op)	test_bit(SCX_OP_IDX(op), (sch)->has_op)
@@ -3654,39 +3655,40 @@ bool scx_allow_ttwu_queue(const struct task_struct *p) 
	return false;

}



/**

 * scx_rcu_cpu_stall - sched_ext RCU CPU stall handler

 *

 * While there are various reasons why RCU CPU stalls can occur on a system

 * 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.

 */

bool scx_rcu_cpu_stall(void)

static __printf(1, 2) bool handle_lockup(const char *fmt, ...)

{

	struct scx_sched *sch;

	va_list args;



	rcu_read_lock();

	guard(rcu)();



	sch = rcu_dereference(scx_root);

	if (unlikely(!sch)) {

		rcu_read_unlock();

	if (unlikely(!sch))

		return false;

	}



	switch (scx_enable_state()) {

	case SCX_ENABLING:

	case SCX_ENABLED:

		break;

		va_start(args, fmt);

		scx_verror(sch, fmt, args);

		va_end(args);

		return true;

	default:

		rcu_read_unlock();

		return false;

	}

}



	scx_error(sch, "RCU CPU stall detected!");

	rcu_read_unlock();



	return true;

/**

 * scx_rcu_cpu_stall - sched_ext RCU CPU stall handler

 *

 * While there are various reasons why RCU CPU stalls can occur on a system

 * 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.

 */

bool scx_rcu_cpu_stall(void)

{

	return handle_lockup("RCU CPU stall detected!");

}



/**
@@ -3701,28 +3703,11 @@ bool scx_rcu_cpu_stall(void) 
 */

void scx_softlockup(u32 dur_s)

{

	struct scx_sched *sch;



	rcu_read_lock();



	sch = rcu_dereference(scx_root);

	if (unlikely(!sch))

		goto out_unlock;



	switch (scx_enable_state()) {

	case SCX_ENABLING:

	case SCX_ENABLED:

		break;

	default:

		goto out_unlock;

	}



	printk_deferred(KERN_ERR "sched_ext: Soft lockup - CPU%d stuck for %us, disabling \"%s\"\n",

			smp_processor_id(), dur_s, scx_root->ops.name);

	if (!handle_lockup("soft lockup - CPU %d stuck for %us", smp_processor_id(), dur_s))

		return;



	scx_error(sch, "soft lockup - CPU#%d stuck for %us", smp_processor_id(), dur_s);

out_unlock:

	rcu_read_unlock();

	printk_deferred(KERN_ERR "sched_ext: Soft lockup - CPU %d stuck for %us, disabling BPF scheduler\n",

			smp_processor_id(), dur_s);

}



/**