On Tue, Feb 13, 2024 at 04:28:59PM +0100, Thomas Gleixner wrote:
>
> From: Frederic Weisbecker <frederic@xxxxxxxxxx>
>
> commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream.
>
> The hrtimers migration on CPU-down hotplug process has been moved
> earlier, before the CPU actually goes to die. This leaves a small window
> of opportunity to queue an hrtimer in a blind spot, leaving it ignored.
>
> For example a practical case has been reported with RCU waking up a
> SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that
> way a sched/rt timer to the local offline CPU.
>
> Make sure such situations never go unnoticed and warn when that happens.
>
> Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
> Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Link: https://lore.kernel.org/r/20240129235646.3171983-4-boqun.feng@xxxxxxxxx
> ---
>
> Backport to 4.19 as tglx has too much spare time...
Now queued up, thanks.
greg k-h
