On Mon, Aug 11, 2014 at 08:55:07PM +0200, Hans de Goede wrote: > Hi, > > On 08/11/2014 08:19 PM, Guenter Roeck wrote: > > On Mon, Aug 11, 2014 at 01:29:26PM +0530, Sanjeev Sharma wrote: > >> spin_is_locked() always return false in uniprocessor configuration and therefore it > >> would be advise to repalce with assert_spin_locked(). > >> > >> Signed-off-by: Sanjeev Sharma <Sanjeev_Sharma@xxxxxxxxxx> > >> --- > >> drivers/usb/storage/uas.c | 8 ++++---- > >> 1 file changed, 4 insertions(+), 4 deletions(-) > >> > >> diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c > >> index 3f42785..8e5877d 100644 > >> --- a/drivers/usb/storage/uas.c > >> +++ b/drivers/usb/storage/uas.c > >> @@ -154,7 +154,7 @@ static void uas_mark_cmd_dead(struct uas_dev_info *devinfo, > >> struct scsi_cmnd *cmnd = container_of(scp, struct scsi_cmnd, SCp); > >> > >> uas_log_cmd_state(cmnd, caller); > >> - WARN_ON_ONCE(!spin_is_locked(&devinfo->lock)); > >> + assert_spin_locked(&devinfo->lock); > > > > Seems to me that replacing WARN_ON_ONCE (which may be annoying but only > > creates a traceback, and only once) with assert_spin_locked (which > > crashes the kernel) is a bit drastic. > > I can see your point, but so far these paranoia checks have never triggered, > and having them trigger _always_ one some uni-processor (which is the reason > for this patch) to me seems the worse problem of the 2. > If those are just paranoia checks, it might make sense to use lockdep_assert_held() to reduce runtime overhead if lockdep debugging is disabled. > Ideally we would have a warn_spin_not_locked or such ... > There is WARN_ON_SMP, which might have been a better choice if the _ONCE isn't that important (which one should think if it is ok to crash the kernel if the problem is seen). Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
