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authorUlrich Obergfell <uobergfe@redhat.com>2015-04-14 15:44:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-14 16:48:59 -0700
commitef246a216b02c604ff465b9a62bb0d2e1ea183a7 (patch)
tree959d6402bd5e193830fd1c8ee270ec9eb34a5a0f /lib/rational.c
parentf54c2274f5515da6bae779c7340cd0dc69d0dd8d (diff)
watchdog: introduce proc_watchdog_common()
Three of four handlers for the watchdog parameters in /proc/sys/kernel essentially have to do the same thing. if the parameter is being read { return the state of the corresponding bit(s) in 'watchdog_enabled' } else { set/clear the state of the corresponding bit(s) in 'watchdog_enabled' update the run state of the lockup detector(s) } Hence, introduce a common function that can be called by those handlers. The callers pass a 'bit mask' to this function to indicate which bit(s) should be set/cleared in 'watchdog_enabled'. This function handles an uncommon race with watchdog_nmi_enable() where a concurrent update of 'watchdog_enabled' is possible. We use 'cmpxchg' to detect the concurrency. [This avoids introducing a new spinlock or a mutex to synchronize updates of 'watchdog_enabled'. Using the same lock or mutex in watchdog thread context and in system call context needs to be considered carefully because it can make the code prone to deadlock situations in connection with parking/unparking the watchdog threads.] Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/rational.c')
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