rcutorture: Also use GP sequence to judge forward progress (119248be) · Commits · 戴 / test

Currently, rcutorture relies solely on the progress of rcu_torture_writer() to judge grace-period forward progress. In theory, this is the gold standard of forward progress, but in practice rcutorture separately detects and reports rcu_torture_writer() stalls. This commit therefore adds the grace-period sequence number (when provided) to the judgment of grace-period forward progress, which makes it easier to distinguish between failure of actual grace periods to progress on the one hand and downstream forward-progress failures on the other. For example, given this change, if rcu_torture_writer() stalls, but rcu_torture_fwd_prog() does not complain, then the grace-period computation is working, which is a hint that the failure lies in callback processing, wakeup of the rcu_torture_writer() kthread, or similar. Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/rcutorture.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -1673,7 +1673,8 @@ static int __init rcu_torture_stall_init(void)
		/* Carry out grace-period forward-progress testing. */
		static int rcu_torture_fwd_prog(void *args)
		{
		unsigned long cvar;
		unsigned long cver;
		unsigned long gps;
		int idx;
		unsigned long stopat;
		bool tested = false;
		@@ -1681,7 +1682,8 @@ static int rcu_torture_fwd_prog(void *args)
		VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
		do {
		schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
		cvar = READ_ONCE(rcu_torture_current_version);
		cver = READ_ONCE(rcu_torture_current_version);
		gps = cur_ops->get_gp_seq();
		stopat = jiffies + cur_ops->stall_dur() / fwd_progress_div;
		while (time_before(jiffies, stopat) && !torture_must_stop()) {
		idx = cur_ops->readlock();
		@@ -1692,8 +1694,9 @@ static int rcu_torture_fwd_prog(void *args)
		}
		if (!time_before(jiffies, stopat) && !torture_must_stop()) {
		tested = true;
		WARN_ON_ONCE(cvar ==
		READ_ONCE(rcu_torture_current_version));
		cver = cver == READ_ONCE(rcu_torture_current_version);
		gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
		WARN_ON_ONCE(cver && gps < 2);
		}
		/* Avoid slow periods, better to test when busy. */
		stutter_wait("rcu_torture_fwd_prog");

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