watchdog: fix barriers when printing backtraces from all CPUs

Any parallel softlockup reports are skipped when one CPU is already
printing backtraces from all CPUs.

The exclusive rights are synchronized using one bit in
soft_lockup_nmi_warn.  There is also one memory barrier that does not make
much sense.

Use two barriers on the right location to prevent mixing two reports.

[[email protected]: use bit lock operations to prevent multiple soft-lockup reports]
  Link: https://lkml.kernel.org/r/YFSVsLGVWMXTvlbk@alley

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Laurence Oberman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vincent Whitchurch <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions