posix-timers: Use a callback for cancel synchronization on PREEMPT_RT

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Posix timer delete retry loops are affected by the same priority inversion
and live lock issues as the other timers.
    
Provide a RT specific synchronization function which keeps a reference to
the timer by holding rcu read lock to prevent the timer from being freed,
dropping the timer lock and invoking the timer specific wait function via a
new callback.
    
This does not yet cover posix CPU timers because they need more special
treatment on PREEMPT_RT.

[ This is folded into the original attempt which did not use a callback. ]

Originally-by: Anna-Maria Gleixenr <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190819143801.656864506@linutronix.de

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This commit is contained in:

Thomas Gleixner 2019-08-02 07:35:59 +02:00

parent 5d99b32a00

commit ec8f954a40

3 changed files with 32 additions and 1 deletions

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14

kernel/time/alarmtimer.c

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18

kernel/time/posix-timers.c

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1

kernel/time/posix-timers.h

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