| Message ID | 37a29c383bff2fb1605241ee6c7c9be3784fb3c6.1613171185.git.skhan@linuxfoundation.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Johannes Berg |
| Headers | show |
| Series | Add lockdep_assert_not_held() | expand |
On Fri, Feb 12, 2021 at 04:28:42PM -0700, Shuah Khan wrote: > +#define lockdep_assert_not_held(l) do { \ > + WARN_ON(debug_locks && lockdep_is_held(l)); \ > + } while (0) > + This thing isn't as straight forward as you might think, but it'll mostly work. Notably this thing will misfire when lockdep_off() is employed. It certainyl needs a comment to explain the subtleties.
On Sun, Feb 14, 2021 at 06:53:01PM +0100, Peter Zijlstra wrote: > On Fri, Feb 12, 2021 at 04:28:42PM -0700, Shuah Khan wrote: > > > +#define lockdep_assert_not_held(l) do { \ > > + WARN_ON(debug_locks && lockdep_is_held(l)); \ > > + } while (0) > > + > > This thing isn't as straight forward as you might think, but it'll > mostly work. > > Notably this thing will misfire when lockdep_off() is employed. It > certainyl needs a comment to explain the subtleties. I think something like so will work, but please double check. diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index b9e9adec73e8..c8b0d292bf8e 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) -#define lockdep_assert_held(l) do { \ - WARN_ON(debug_locks && !lockdep_is_held(l)); \ +#define lockdep_assert_held(l) do { \ + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \ } while (0) -#define lockdep_assert_held_write(l) do { \ +#define lockdep_assert_not_held(l) do { \ + WARN_ON(debug_locks && lockdep_is_held(l) == 1)); \ + } while (0) + +#define lockdep_assert_held_write(l) do { \ WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \ } while (0) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index c1418b47f625..983ba206f7b2 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -5467,7 +5467,7 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read) int ret = 0; if (unlikely(!lockdep_enabled())) - return 1; /* avoid false negative lockdep_assert_held() */ + return -1; /* avoid false negative lockdep_assert_held() */ raw_local_irq_save(flags); check_flags(flags);
On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote: > > I think something like so will work, but please double check. Yeah, that looks better. > +++ b/include/linux/lockdep.h > @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); > > #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) > > -#define lockdep_assert_held(l) do { \ > - WARN_ON(debug_locks && !lockdep_is_held(l)); \ > +#define lockdep_assert_held(l) do { \ > + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \ > } while (0) That doesn't really need to change? It's the same. > -#define lockdep_assert_held_write(l) do { \ > +#define lockdep_assert_not_held(l) do { \ > + WARN_ON(debug_locks && lockdep_is_held(l) == 1)); \ > + } while (0) > + > +#define lockdep_assert_held_write(l) do { \ > WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \ > } while (0) > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index c1418b47f625..983ba206f7b2 100644 > --- a/kernel/locking/lockdep. > +++ b/kernel/locking/lockdep.c > @@ -5467,7 +5467,7 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read) > int ret = 0; > > if (unlikely(!lockdep_enabled())) > - return 1; /* avoid false negative lockdep_assert_held() */ > + return -1; /* avoid false negative lockdep_assert_held() */ Maybe add lockdep_assert_not_held() to the comment, to explain the -1 (vs non-zero)? johannes
On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote: > On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote: > > > > I think something like so will work, but please double check. > > Yeah, that looks better. > > > +++ b/include/linux/lockdep.h > > @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); > > > > #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) > > > > -#define lockdep_assert_held(l) do { \ > > - WARN_ON(debug_locks && !lockdep_is_held(l)); \ > > +#define lockdep_assert_held(l) do { \ > > + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \ > > } while (0) > > That doesn't really need to change? It's the same. Correct, but I found it more symmetric vs the not implementation below. > > -#define lockdep_assert_held_write(l) do { \ > > +#define lockdep_assert_not_held(l) do { \ > > + WARN_ON(debug_locks && lockdep_is_held(l) == 1)); \ > > + } while (0) > > + > > +#define lockdep_assert_held_write(l) do { \ > > WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \ > > } while (0) > > > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > > index c1418b47f625..983ba206f7b2 100644 > > --- a/kernel/locking/lockdep. > > +++ b/kernel/locking/lockdep.c > > @@ -5467,7 +5467,7 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read) > > int ret = 0; > > > > if (unlikely(!lockdep_enabled())) > > - return 1; /* avoid false negative lockdep_assert_held() */ > > + return -1; /* avoid false negative lockdep_assert_held() */ > > Maybe add lockdep_assert_not_held() to the comment, to explain the -1 > (vs non-zero)? Yeah, or frob a '*' in there.
On Mon, 2021-02-15 at 17:04 +0100, Peter Zijlstra wrote: > On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote: > > On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote: > > > I think something like so will work, but please double check. > > > > Yeah, that looks better. > > > > > +++ b/include/linux/lockdep.h > > > @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); > > > > > > #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) > > > > > > -#define lockdep_assert_held(l) do { \ > > > - WARN_ON(debug_locks && !lockdep_is_held(l)); \ > > > +#define lockdep_assert_held(l) do { \ > > > + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \ > > > } while (0) > > > > That doesn't really need to change? It's the same. > > Correct, but I found it more symmetric vs the not implementation below. Fair enough. One might argue that you should have an enum lockdep_lock_state { LOCK_STATE_NOT_HELD, /* 0 now */ LOCK_STATE_HELD, /* 1 now */ LOCK_STATE_UNKNOWN, /* -1 with your patch but might as well be 2 */ }; :) johannes
On 2/15/21 9:10 AM, Johannes Berg wrote: > On Mon, 2021-02-15 at 17:04 +0100, Peter Zijlstra wrote: >> On Mon, Feb 15, 2021 at 02:12:30PM +0100, Johannes Berg wrote: >>> On Mon, 2021-02-15 at 11:44 +0100, Peter Zijlstra wrote: >>>> I think something like so will work, but please double check. >>> >>> Yeah, that looks better. >>> >>>> +++ b/include/linux/lockdep.h >>>> @@ -294,11 +294,15 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); >>>> >>>> #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) >>>> >>>> -#define lockdep_assert_held(l) do { \ >>>> - WARN_ON(debug_locks && !lockdep_is_held(l)); \ >>>> +#define lockdep_assert_held(l) do { \ >>>> + WARN_ON(debug_locks && lockdep_is_held(l) == 0)); \ >>>> } while (0) >>> >>> That doesn't really need to change? It's the same. >> >> Correct, but I found it more symmetric vs the not implementation below. > > Fair enough. One might argue that you should have an > > enum lockdep_lock_state { > LOCK_STATE_NOT_HELD, /* 0 now */ > LOCK_STATE_HELD, /* 1 now */ > LOCK_STATE_UNKNOWN, /* -1 with your patch but might as well be 2 */ > }; > > :) > Thank you both. Picking this back up. Will send v2 incorporating your comments and suggestions. thanks, -- Shuah
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index b9e9adec73e8..567e3a1a27ce 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -294,6 +294,10 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie); #define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0) +#define lockdep_assert_not_held(l) do { \ + WARN_ON(debug_locks && lockdep_is_held(l)); \ + } while (0) + #define lockdep_assert_held(l) do { \ WARN_ON(debug_locks && !lockdep_is_held(l)); \ } while (0) @@ -383,8 +387,9 @@ extern int lock_is_held(const void *); extern int lockdep_is_held(const void *); #define lockdep_is_held_type(l, r) (1) +#define lockdep_assert_not_held(l) do { (void)(l); } while (0) #define lockdep_assert_held(l) do { (void)(l); } while (0) -#define lockdep_assert_held_write(l) do { (void)(l); } while (0) +#define lockdep_assert_held_write(l) do { (void)(l); } while (0) #define lockdep_assert_held_read(l) do { (void)(l); } while (0) #define lockdep_assert_held_once(l) do { (void)(l); } while (0)
Some kernel functions must not be called holding a specific lock. Doing so could lead to locking problems. Currently these routines call lock_is_held() to check for lock hold followed by WARN_ON. Adding a common lockdep interface will help reduce the duplication of this logic in the rest of the kernel. Add lockdep_assert_not_held() to be used in these functions to detect incorrect calls while holding a lock. lockdep_assert_not_held() provides the opposite functionality of lockdep_assert_held() which is used to assert calls that require holding a specific lock. The need for lockdep_assert_not_held() came up in a discussion on ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples of functions that can use lockdep_assert_not_held(). Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/ Signed-off-by: Shuah Khan <skhan@linuxfoundation.org> --- include/linux/lockdep.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)