Commit a80be428 authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Paul E. McKenney
Browse files

rcu: Do not disable GP stall detection in rcu_cpu_stall_reset() 



rcu_cpu_stall_reset() is one of the functions virtual CPUs
execute during VM resume in order to handle jiffies skew
that can trigger false positive stall warnings. Paul has
pointed out that this approach is problematic because
rcu_cpu_stall_reset() disables RCU grace period stall-detection
virtually forever, while in fact it can just restart the
stall-detection timeout.

Suggested-by: default avatar"Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: default avatarSigned-off-by: Paul E. McKenney <paulmck@kernel.org>
parent ccfc9dd6

kernel/rcu/tree_stall.h

+3 −6
Original line number Diff line number Diff line
@@ -119,17 +119,14 @@ static void panic_on_rcu_stall(void) 
}



/**

 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period

 *

 * Set the stall-warning timeout way off into the future, thus preventing

 * any RCU CPU stall-warning messages from appearing in the current set of

 * RCU grace periods.

 * rcu_cpu_stall_reset - restart stall-warning timeout for current grace period

 *

 * The caller must disable hard irqs.

 */

void rcu_cpu_stall_reset(void)

{

	WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2);

	WRITE_ONCE(rcu_state.jiffies_stall,

		   jiffies + rcu_jiffies_till_stall_check());

}



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