| Message ID | 6b8f405145d3d57a8026dc61ca3f1ae70d690990.1682847325.git.christophe.jaillet@wanadoo.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | spi: Use non-atomic xxx_bit() functions | expand |
On Sun, Apr 30, 2023 at 11:35:35AM +0200, Christophe JAILLET wrote: > Accesses to 'minors' are guarded by the 'device_list_lock' mutex. So, it is > safe to use the non-atomic version of (set|clear)_bit() in the > corresponding sections. Is it a problem to use the atomic version? > if (status == 0) { > - set_bit(minor, minors); > + __set_bit(minor, minors); > list_add(&spidev->device_entry, &device_list); The __ usually means something is the more complicated and less preferred API.
Le 30/04/2023 à 17:49, Mark Brown a écrit : > On Sun, Apr 30, 2023 at 11:35:35AM +0200, Christophe JAILLET wrote: > >> Accesses to 'minors' are guarded by the 'device_list_lock' mutex. So, it is >> safe to use the non-atomic version of (set|clear)_bit() in the >> corresponding sections. > > Is it a problem to use the atomic version? Not at all. It just wastes a few cycles (in a place where it doesn't matter). I spotted it while looking for some other patterns, so I sent a patch for it. > >> if (status == 0) { >> - set_bit(minor, minors); >> + __set_bit(minor, minors); >> list_add(&spidev->device_entry, &device_list); > > The __ usually means something is the more complicated and less > preferred API. Ok, let keep things as-is and simple then. Performance doesn't matter here, anyway. CJ
diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index 39d94c850839..132fecc02eba 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -812,7 +812,7 @@ static int spidev_probe(struct spi_device *spi) status = -ENODEV; } if (status == 0) { - set_bit(minor, minors); + __set_bit(minor, minors); list_add(&spidev->device_entry, &device_list); } mutex_unlock(&device_list_lock); @@ -840,7 +840,7 @@ static void spidev_remove(struct spi_device *spi) list_del(&spidev->device_entry); device_destroy(spidev_class, spidev->devt); - clear_bit(MINOR(spidev->devt), minors); + __clear_bit(MINOR(spidev->devt), minors); if (spidev->users == 0) kfree(spidev); mutex_unlock(&device_list_lock);
Accesses to 'minors' are guarded by the 'device_list_lock' mutex. So, it is safe to use the non-atomic version of (set|clear)_bit() in the corresponding sections. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- drivers/spi/spidev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)