Commit b367017c authored by Sven Schnelle's avatar Sven Schnelle Committed by Alexander Gordeev
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s390/stp: Remove udelay from stp_sync_clock() 



When an stp sync check is handled on a system with multiple
cpus each cpu gets a machine check but only the first one
actually handles the sync operation. All other CPUs spin
waiting for the first one to finish with a short udelay().
But udelay can't be used here as the first CPU modifies tod_clock_base
before performing the sync op. During this timeframe
get_tod_clock_monotonic() might return a non-monotonic time.

The time spent waiting should be very short and udelay is a busy loop
anyways, therefore simply remove the udelay.

Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
parent 7cf636c9

arch/s390/kernel/time.c

+1 −1
Original line number Diff line number Diff line
@@ -580,7 +580,7 @@ static int stp_sync_clock(void *data) 
		atomic_dec(&sync->cpus);

		/* Wait for in_sync to be set. */

		while (READ_ONCE(sync->in_sync) == 0)

			__udelay(1);

			;

	}

	if (sync->in_sync != 1)

		/* Didn't work. Clear per-cpu in sync bit again. */