On Mon, Apr 19, 2021 at 8:32 AM Tzung-Bi Shih [off-list ref] wrote:

Commit 42a46434e9b1 ("pinctrl: add lock in mtk_rmw function.") uses
mutex lock in mtk_rmw.  However the function is possible called from
atomic context.

For example call trace:

Please, shrink it to the necessary minimum.

  mutex_lock+0x28/0x64
  mtk_rmw+0x38/0x80
  mtk_hw_set_value+0x100/0x138
  mtk_gpio_set+0x48/0x58
  gpiod_set_raw_value_commit+0xf4/0x110
  gpiod_set_value_nocheck+0x4c/0x80
  gpiod_set_value+0x4c/0x6c
  max98357a_daiops_trigger+0x8c/0x9c
  soc_pcm_trigger+0x5c/0x10c

The max98357a_daiops_trigger() could run in either atomic or non-atomic
context.  As a result, dmesg shows some similar messages: "BUG: sleeping
function called from invalid context at kernel/locking/mutex.c:254".

Uses spin lock in mtk_rmw instead.

It's nice, but now the question is, can you have this function be
called in a non-IRQ context concurrently with IRQ accessing registers?


-- 
With Best Regards,
Andy Shevchenko

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel