Re: [PATCH] stackdepot: fix stack_depot_save_flags() in NMI context

[Sebastian Andrzej Siewior]

On 2024-11-22 16:39:47 [+0100], Marco Elver wrote:
> Per documentation, stack_depot_save_flags() was meant to be usable from
> NMI context if STACK_DEPOT_FLAG_CAN_ALLOC is unset. However, it still
> would try to take the pool_lock in an attempt to save a stack trace in
> the current pool (if space is available).
> 
> This could result in deadlock if an NMI is handled while pool_lock is
> already held. To avoid deadlock, only try to take the lock in NMI
> context and give up if unsuccessful.
> 
> The documentation is fixed to clearly convey this.
> 
> Link: https://lkml.kernel.org/r/Z0CcyfbPqmxJ9uJH@xxxxxxxxxxxxxxxx
> Fixes: 4434a56ec209 ("stackdepot: make fast paths lock-less again")
> Reported-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Marco Elver <elver@xxxxxxxxxx>

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

Sebastian