stop-machine: Add comment for rcu_momentary_eqs()

Add a comment to explain the purpose of the rcu_momentary_eqs() call
from multi_cpu_stop(), which is to suppress false-positive RCU CPU
stall warnings.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/87wmeuanti.ffs@tglx/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 8896d844d738ffdf50bd9e7b7ad2218ae2573f05..5d2d0562115b31701dc67d9760e6715fce75a90c 100644 (file)
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -250,6 +250,7 @@ static int multi_cpu_stop(void *data)
                         * be detected and reported on their side.
                         */
                        touch_nmi_watchdog();
+                       /* Also suppress RCU CPU stall warnings. */
                        rcu_momentary_eqs();
                }
        } while (curstate != MULTI_STOP_EXIT);