Re: [PATCH v3 7/7] zram: Use local lock to protect per-CPU data

[Minchan Kim]

On Wed, May 27, 2020 at 10:11:19PM +0200, Sebastian Andrzej Siewior wrote:
> From: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
> 
> The zcomp driver uses per-CPU compression. The per-CPU data pointer is
> acquired with get_cpu_ptr() which implicitly disables preemption.
> It allocates memory inside the preempt disabled region which conflicts
> with the PREEMPT_RT semantics.
> 
> Replace the implicit preemption control with an explicit local lock.
> This allows RT kernels to substitute it with a real per CPU lock, which
> serializes the access but keeps the code section preemptible. On non RT
> kernels this maps to preempt_disable() as before, i.e. no functional
> change.
> 
> [bigeasy: Use local_lock(), description, drop reordering]
> 
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
> Signed-off-by: Mike Galbraith <umgwanakikbuti@xxxxxxxxx>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>