| Date | Thu, 4 May 2023 19:06:50 +0200 | From | Frederic Weisbecker <> | Subject | Re: [patch 01/20] posix-timers: Prevent RT livelock in itimer_delete() |
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Le Tue, Apr 25, 2023 at 08:48:56PM +0200, Thomas Gleixner a écrit : > itimer_delete() has a retry loop when the timer is concurrently expired. On > non-RT kernels this just spin-waits until the timer callback has > completed. On RT kernels this is a potential livelock when the exiting task > preempted the hrtimer soft interrupt. > > This only affects hrtimer based timers as Posix CPU timers cannot be > concurrently expired. For CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y this is > obviously impossible as the task cannot run task work and exit at the same > time. The CONFIG_POSIX_CPU_TIMERS_TASK_WORK=n (only non-RT) is prevented > because interrupts are disabled.
But the owner of the timer is not the same as the target of the timer, right?
Though I seem to remember that we forbid setting a timer to a target outside the current process, in which case the owner and the target are the same at this exit stage. But I can't remember what enforces that permission in pid_for_clock()...
Thanks.
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