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rcutorture: Avoid printing cpu=-1 for no-fault RCU boost failure

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If a CPU runs throughout the stalled grace period without passing
through a quiescent state, RCU priority boosting cannot help.
The rcu_torture_boost_failed() function therefore prints a message
flagging the first such CPU.  However, if the stall was instead due to
(for example) RCU's grace-period kthread being starved of CPU, there will
be no such CPU, causing rcu_check_boost_fail() to instead pass back -1
through its cpup CPU-pointer parameter.

Therefore, the current message complains about a mythical CPU -1.

This commit therefore checks for this situation, and notes that all CPUs
have passed through a quiescent state.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
This commit is contained in:
Paul E. McKenney
2024-10-09 11:02:53 -07:00
committed by Frederic Weisbecker
parent ff9ba8db87
commit 80e935c8c1
1 changed files with 7 additions and 2 deletions
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kernel/rcu/rcutorture.c
+7 -2
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@@ -1059,8 +1059,13 @@ static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long *star
// At most one persisted message per boost test.
j = jiffies;
lp = READ_ONCE(last_persist);
if (time_after(j, lp + mininterval) && cmpxchg(&last_persist, lp, j) == lp)
pr_info("Boost inversion persisted: No QS from CPU %d\n", cpu);
if (time_after(j, lp + mininterval) &&
cmpxchg(&last_persist, lp, j) == lp) {
if (cpu < 0)
pr_info("Boost inversion persisted: QS from all CPUs\n");
else
pr_info("Boost inversion persisted: No QS from CPU %d\n", cpu);
}
return false; // passed on a technicality
}
VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");