| Message ID | 1407731491-22446-1-git-send-email-linux@roeck-us.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hello Roeck, This should be replaced everywhere in driver.what do you say ? Regards Sanjeev Sharma On Mon, Aug 11, 2014 at 10:01 AM, Guenter Roeck <linux@roeck-us.net> wrote: > spin_is_locked() always returns false in uniprocessor configurations > and can therefore not be used with BUG_ON. Replace it with > assert_spin_locked(), which exists for that very purpose. > > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > --- > drivers/gpu/drm/msm/mdp/mdp_kms.c | 2 +- > drivers/gpu/drm/nouveau/core/core/event.c | 4 ++-- > drivers/gpu/drm/nouveau/core/core/notify.c | 2 +- > drivers/gpu/drm/omapdrm/omap_irq.c | 2 +- > 4 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/msm/mdp/mdp_kms.c > b/drivers/gpu/drm/msm/mdp/mdp_kms.c > index 03455b6..92a1531 100644 > --- a/drivers/gpu/drm/msm/mdp/mdp_kms.c > +++ b/drivers/gpu/drm/msm/mdp/mdp_kms.c > @@ -34,7 +34,7 @@ static void update_irq(struct mdp_kms *mdp_kms) > struct mdp_irq *irq; > uint32_t irqmask = mdp_kms->vblank_mask; > > - BUG_ON(!spin_is_locked(&list_lock)); > + assert_spin_locked(&list_lock); > > list_for_each_entry(irq, &mdp_kms->irq_list, node) > irqmask |= irq->irqmask; > diff --git a/drivers/gpu/drm/nouveau/core/core/event.c > b/drivers/gpu/drm/nouveau/core/core/event.c > index 0540a48..9327117 100644 > --- a/drivers/gpu/drm/nouveau/core/core/event.c > +++ b/drivers/gpu/drm/nouveau/core/core/event.c > @@ -26,7 +26,7 @@ > void > nvkm_event_put(struct nvkm_event *event, u32 types, int index) > { > - BUG_ON(!spin_is_locked(&event->refs_lock)); > + assert_spin_locked(&event->refs_lock); > while (types) { > int type = __ffs(types); types &= ~(1 << type); > if (--event->refs[index * event->types_nr + type] == 0) { > @@ -39,7 +39,7 @@ nvkm_event_put(struct nvkm_event *event, u32 types, int > index) > void > nvkm_event_get(struct nvkm_event *event, u32 types, int index) > { > - BUG_ON(!spin_is_locked(&event->refs_lock)); > + assert_spin_locked(&event->refs_lock); > while (types) { > int type = __ffs(types); types &= ~(1 << type); > if (++event->refs[index * event->types_nr + type] == 1) { > diff --git a/drivers/gpu/drm/nouveau/core/core/notify.c > b/drivers/gpu/drm/nouveau/core/core/notify.c > index 76adb81..f70dbc4 100644 > --- a/drivers/gpu/drm/nouveau/core/core/notify.c > +++ b/drivers/gpu/drm/nouveau/core/core/notify.c > @@ -98,7 +98,7 @@ nvkm_notify_send(struct nvkm_notify *notify, void *data, > u32 size) > struct nvkm_event *event = notify->event; > unsigned long flags; > > - BUG_ON(!spin_is_locked(&event->list_lock)); > + assert_spin_locked(&event->list_lock); > BUG_ON(size != notify->size); > > spin_lock_irqsave(&event->refs_lock, flags); > diff --git a/drivers/gpu/drm/omapdrm/omap_irq.c > b/drivers/gpu/drm/omapdrm/omap_irq.c > index f035d2b..3eb097e 100644 > --- a/drivers/gpu/drm/omapdrm/omap_irq.c > +++ b/drivers/gpu/drm/omapdrm/omap_irq.c > @@ -34,7 +34,7 @@ static void omap_irq_update(struct drm_device *dev) > struct omap_drm_irq *irq; > uint32_t irqmask = priv->vblank_mask; > > - BUG_ON(!spin_is_locked(&list_lock)); > + assert_spin_locked(&list_lock); > > list_for_each_entry(irq, &priv->irq_list, node) > irqmask |= irq->irqmask; > -- > 1.9.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
Hello David, Here is the old discussion carried out on this. http://linux-kernel.2935.n7.nabble.com/Is-spin-is-locked-safe-to-use-with-BUG-ON-WARN-ON-td654800.html#a921802 Regards Sanjeev Sharma On Mon, Aug 11, 2014 at 5:31 PM, sanjeev sharma <sanjeevsharmaengg@gmail.com > wrote: > Hello David, > > Do you see any problem in replacing with assert_spin_locked() and here is > old discusion around the > > > > On Mon, Aug 11, 2014 at 5:15 PM, David Rientjes <rientjes@google.com> > wrote: > >> On Sun, 10 Aug 2014, Guenter Roeck wrote: >> >> > spin_is_locked() always returns false in uniprocessor configurations >> > and can therefore not be used with BUG_ON. Replace it with >> > assert_spin_locked(), which exists for that very purpose. >> > >> >> It may be helpful to assess whether any of these sites should be converted >> to lockdep_assert_held() so they have no cost when lockdep isn't enabled >> but still reveal problems when debugging. >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > >
Thanks all and I replaced with lockdep_assert_held() which seems less overhead. Regards Sanjeev Sharma On Tue, Aug 12, 2014 at 5:08 AM, David Rientjes <rientjes@google.com> wrote: > On Mon, 11 Aug 2014, Rob Clark wrote: > > > > I'm suggesting that if you don't want to incur the cost of the > conditional > > > everytime you call a certain function with assert_spin_locked() that > you > > > could covert these to lockdep_assert_held() so the check is only done > when > > > lockdep is enabled for debugging. > > > > not sure about the nouveau parts, but for the omap and msm hunks, this > > code getting called at potentially vblank rate (so maybe once or twice > > per ~16ms).. and lockdep has considerable overhead (for a gpu driver) > > so I don't always have it enabled. So it sounds like for those two at > > least assert_spin_locked() is a better option. > > > > Unless there's a bug, assert_spin_locked() is just going to incur an > unnecessary cost every time it is called at runtime. My suggestion was to > limit that check only to debugging kernels that include enabling lockdep > when tracking down problems rather than needlessly evaluating the > conditional every time when there are no bugs. >
On Mon, Aug 11, 2014 at 04:38:50PM -0700, David Rientjes wrote: > On Mon, 11 Aug 2014, Rob Clark wrote: > > > > I'm suggesting that if you don't want to incur the cost of the conditional > > > everytime you call a certain function with assert_spin_locked() that you > > > could covert these to lockdep_assert_held() so the check is only done when > > > lockdep is enabled for debugging. > > > > not sure about the nouveau parts, but for the omap and msm hunks, this > > code getting called at potentially vblank rate (so maybe once or twice > > per ~16ms).. and lockdep has considerable overhead (for a gpu driver) > > so I don't always have it enabled. So it sounds like for those two at > > least assert_spin_locked() is a better option. > > > > Unless there's a bug, assert_spin_locked() is just going to incur an > unnecessary cost every time it is called at runtime. My suggestion was to > limit that check only to debugging kernels that include enabling lockdep > when tracking down problems rather than needlessly evaluating the > conditional every time when there are no bugs. My experience with gpu drivers (i915) has been that hw and the software running it is varied enough that almost always it's better to unconditionally enable this stuff. I much prefer assert_spin_locked and friends over the lockdep versions since enabling full lockdep is not something you usually do. Especially not normal users, and we rely upon them for testing the old stuff. Furthermore for the modeset code the overhead is totally irrelevant since we're doing metric piles of register reads and writes in there anyway. -Daniel
yes you are absolutely correct and the change I have done in other area i.e drivers/usb/storage/uas.c.In gpu drivers assert_spin_locked() make more sense. Regards Sanjeev Sharma On Tue, Aug 12, 2014 at 12:25 PM, Daniel Vetter <daniel@ffwll.ch> wrote: > On Mon, Aug 11, 2014 at 04:38:50PM -0700, David Rientjes wrote: > > On Mon, 11 Aug 2014, Rob Clark wrote: > > > > > > I'm suggesting that if you don't want to incur the cost of the > conditional > > > > everytime you call a certain function with assert_spin_locked() that > you > > > > could covert these to lockdep_assert_held() so the check is only > done when > > > > lockdep is enabled for debugging. > > > > > > not sure about the nouveau parts, but for the omap and msm hunks, this > > > code getting called at potentially vblank rate (so maybe once or twice > > > per ~16ms).. and lockdep has considerable overhead (for a gpu driver) > > > so I don't always have it enabled. So it sounds like for those two at > > > least assert_spin_locked() is a better option. > > > > > > > Unless there's a bug, assert_spin_locked() is just going to incur an > > unnecessary cost every time it is called at runtime. My suggestion was > to > > limit that check only to debugging kernels that include enabling lockdep > > when tracking down problems rather than needlessly evaluating the > > conditional every time when there are no bugs. > > My experience with gpu drivers (i915) has been that hw and the software > running it is varied enough that almost always it's better to > unconditionally enable this stuff. I much prefer assert_spin_locked and > friends over the lockdep versions since enabling full lockdep is not > something you usually do. Especially not normal users, and we rely upon > them for testing the old stuff. Furthermore for the modeset code the > overhead is totally irrelevant since we're doing metric piles of register > reads and writes in there anyway. > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch >
>ssert_spin_locked() is a better option. >> > > >> > >> > Unless there's a bug, assert_spin_locked() is just going to incur an >> > unnecessary cost every time it is called at runtime. My suggestion was >> > to >> > limit that check only to debugging kernels that include enabling lockdep >> > when tracking down problems rather than needlessly evaluating the >> > conditional every time when there are no bugs. >> >> My experience with gpu drivers (i915) has been that hw and the software >> running it is varied enough that almost always it's better to >> unconditionally enable this stuff. I much prefer assert_spin_locked and >> friends over the lockdep versions since enabling full lockdep is not >> something you usually do. Especially not normal users, and we rely upon >> them for testing the old stuff. Furthermore for the modeset code the >> overhead is totally irrelevant since we're doing metric piles of register >> reads and writes in there anyway. Did anything translate into an R-b here? Dave.
diff --git a/drivers/gpu/drm/msm/mdp/mdp_kms.c b/drivers/gpu/drm/msm/mdp/mdp_kms.c index 03455b6..92a1531 100644 --- a/drivers/gpu/drm/msm/mdp/mdp_kms.c +++ b/drivers/gpu/drm/msm/mdp/mdp_kms.c @@ -34,7 +34,7 @@ static void update_irq(struct mdp_kms *mdp_kms) struct mdp_irq *irq; uint32_t irqmask = mdp_kms->vblank_mask; - BUG_ON(!spin_is_locked(&list_lock)); + assert_spin_locked(&list_lock); list_for_each_entry(irq, &mdp_kms->irq_list, node) irqmask |= irq->irqmask; diff --git a/drivers/gpu/drm/nouveau/core/core/event.c b/drivers/gpu/drm/nouveau/core/core/event.c index 0540a48..9327117 100644 --- a/drivers/gpu/drm/nouveau/core/core/event.c +++ b/drivers/gpu/drm/nouveau/core/core/event.c @@ -26,7 +26,7 @@ void nvkm_event_put(struct nvkm_event *event, u32 types, int index) { - BUG_ON(!spin_is_locked(&event->refs_lock)); + assert_spin_locked(&event->refs_lock); while (types) { int type = __ffs(types); types &= ~(1 << type); if (--event->refs[index * event->types_nr + type] == 0) { @@ -39,7 +39,7 @@ nvkm_event_put(struct nvkm_event *event, u32 types, int index) void nvkm_event_get(struct nvkm_event *event, u32 types, int index) { - BUG_ON(!spin_is_locked(&event->refs_lock)); + assert_spin_locked(&event->refs_lock); while (types) { int type = __ffs(types); types &= ~(1 << type); if (++event->refs[index * event->types_nr + type] == 1) { diff --git a/drivers/gpu/drm/nouveau/core/core/notify.c b/drivers/gpu/drm/nouveau/core/core/notify.c index 76adb81..f70dbc4 100644 --- a/drivers/gpu/drm/nouveau/core/core/notify.c +++ b/drivers/gpu/drm/nouveau/core/core/notify.c @@ -98,7 +98,7 @@ nvkm_notify_send(struct nvkm_notify *notify, void *data, u32 size) struct nvkm_event *event = notify->event; unsigned long flags; - BUG_ON(!spin_is_locked(&event->list_lock)); + assert_spin_locked(&event->list_lock); BUG_ON(size != notify->size); spin_lock_irqsave(&event->refs_lock, flags); diff --git a/drivers/gpu/drm/omapdrm/omap_irq.c b/drivers/gpu/drm/omapdrm/omap_irq.c index f035d2b..3eb097e 100644 --- a/drivers/gpu/drm/omapdrm/omap_irq.c +++ b/drivers/gpu/drm/omapdrm/omap_irq.c @@ -34,7 +34,7 @@ static void omap_irq_update(struct drm_device *dev) struct omap_drm_irq *irq; uint32_t irqmask = priv->vblank_mask; - BUG_ON(!spin_is_locked(&list_lock)); + assert_spin_locked(&list_lock); list_for_each_entry(irq, &priv->irq_list, node) irqmask |= irq->irqmask;
spin_is_locked() always returns false in uniprocessor configurations and can therefore not be used with BUG_ON. Replace it with assert_spin_locked(), which exists for that very purpose. Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- drivers/gpu/drm/msm/mdp/mdp_kms.c | 2 +- drivers/gpu/drm/nouveau/core/core/event.c | 4 ++-- drivers/gpu/drm/nouveau/core/core/notify.c | 2 +- drivers/gpu/drm/omapdrm/omap_irq.c | 2 +- 4 files changed, 5 insertions(+), 5 deletions(-)