| Message ID | 20201030142500.5464-3-jgross@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/locking: fix and enhance lock debugging | expand |
On 30.10.2020 15:25, Juergen Gross wrote: > --- a/xen/include/xen/rwlock.h > +++ b/xen/include/xen/rwlock.h > @@ -65,7 +65,11 @@ static inline int _read_trylock(rwlock_t *lock) > * arch_lock_acquire_barrier(). > */ > if ( likely(_can_read_lock(cnts)) ) > + { > + check_lock(&lock->lock.debug, true); > return 1; > + } Why not unconditionally earlier in the function? > @@ -87,7 +91,10 @@ static inline void _read_lock(rwlock_t *lock) > * arch_lock_acquire_barrier(). > */ > if ( likely(_can_read_lock(cnts)) ) > + { > + check_lock(&lock->lock.debug, false); > return; > + } > > /* The slowpath will decrement the reader count, if necessary. */ > queue_read_lock_slowpath(lock); I guess doing so here and ... > @@ -162,7 +169,10 @@ static inline void _write_lock(rwlock_t *lock) > * arch_lock_acquire_barrier(). > */ > if ( atomic_cmpxchg(&lock->cnts, 0, _write_lock_val()) == 0 ) > + { > + check_lock(&lock->lock.debug, false); > return; > + } > > queue_write_lock_slowpath(lock); ... here is okay, as the slow paths have checks anyway. > @@ -205,6 +215,8 @@ static inline int _write_trylock(rwlock_t *lock) > return 0; > } > > + check_lock(&lock->lock.debug, true); But here I again think it wants moving up. Jan
On 30.10.20 16:10, Jan Beulich wrote: > On 30.10.2020 15:25, Juergen Gross wrote: >> --- a/xen/include/xen/rwlock.h >> +++ b/xen/include/xen/rwlock.h >> @@ -65,7 +65,11 @@ static inline int _read_trylock(rwlock_t *lock) >> * arch_lock_acquire_barrier(). >> */ >> if ( likely(_can_read_lock(cnts)) ) >> + { >> + check_lock(&lock->lock.debug, true); >> return 1; >> + } > > Why not unconditionally earlier in the function? Its trylock, so we don't want to call check_lock() without having got the lock. > >> @@ -87,7 +91,10 @@ static inline void _read_lock(rwlock_t *lock) >> * arch_lock_acquire_barrier(). >> */ >> if ( likely(_can_read_lock(cnts)) ) >> + { >> + check_lock(&lock->lock.debug, false); >> return; >> + } >> >> /* The slowpath will decrement the reader count, if necessary. */ >> queue_read_lock_slowpath(lock); > > I guess doing so here and ... > >> @@ -162,7 +169,10 @@ static inline void _write_lock(rwlock_t *lock) >> * arch_lock_acquire_barrier(). >> */ >> if ( atomic_cmpxchg(&lock->cnts, 0, _write_lock_val()) == 0 ) >> + { >> + check_lock(&lock->lock.debug, false); >> return; >> + } >> >> queue_write_lock_slowpath(lock); > > ... here is okay, as the slow paths have checks anyway. > >> @@ -205,6 +215,8 @@ static inline int _write_trylock(rwlock_t *lock) >> return 0; >> } >> >> + check_lock(&lock->lock.debug, true); > > But here I again think it wants moving up. No, another trylock. Juergen
On 30.10.20 16:13, Jürgen Groß wrote: > On 30.10.20 16:10, Jan Beulich wrote: >> On 30.10.2020 15:25, Juergen Gross wrote: >>> --- a/xen/include/xen/rwlock.h >>> +++ b/xen/include/xen/rwlock.h >>> @@ -65,7 +65,11 @@ static inline int _read_trylock(rwlock_t *lock) >>> * arch_lock_acquire_barrier(). >>> */ >>> if ( likely(_can_read_lock(cnts)) ) >>> + { >>> + check_lock(&lock->lock.debug, true); >>> return 1; >>> + } >> >> Why not unconditionally earlier in the function? > > Its trylock, so we don't want to call check_lock() without having > got the lock. Hmm, OTOH we do so for spinlocks, too. So maybe its really better to move it up. Juergen
diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c index 54f0c55dc2..acb3f86339 100644 --- a/xen/common/spinlock.c +++ b/xen/common/spinlock.c @@ -13,7 +13,7 @@ static atomic_t spin_debug __read_mostly = ATOMIC_INIT(0); -static void check_lock(union lock_debug *debug, bool try) +void check_lock(union lock_debug *debug, bool try) { bool irq_safe = !local_irq_is_enabled(); @@ -108,7 +108,6 @@ void spin_debug_disable(void) #else /* CONFIG_DEBUG_LOCKS */ -#define check_lock(l, t) ((void)0) #define check_barrier(l) ((void)0) #define got_lock(l) ((void)0) #define rel_lock(l) ((void)0) diff --git a/xen/include/xen/rwlock.h b/xen/include/xen/rwlock.h index 427664037a..c302644705 100644 --- a/xen/include/xen/rwlock.h +++ b/xen/include/xen/rwlock.h @@ -65,7 +65,11 @@ static inline int _read_trylock(rwlock_t *lock) * arch_lock_acquire_barrier(). */ if ( likely(_can_read_lock(cnts)) ) + { + check_lock(&lock->lock.debug, true); return 1; + } + atomic_sub(_QR_BIAS, &lock->cnts); } preempt_enable(); @@ -87,7 +91,10 @@ static inline void _read_lock(rwlock_t *lock) * arch_lock_acquire_barrier(). */ if ( likely(_can_read_lock(cnts)) ) + { + check_lock(&lock->lock.debug, false); return; + } /* The slowpath will decrement the reader count, if necessary. */ queue_read_lock_slowpath(lock); @@ -162,7 +169,10 @@ static inline void _write_lock(rwlock_t *lock) * arch_lock_acquire_barrier(). */ if ( atomic_cmpxchg(&lock->cnts, 0, _write_lock_val()) == 0 ) + { + check_lock(&lock->lock.debug, false); return; + } queue_write_lock_slowpath(lock); /* @@ -205,6 +215,8 @@ static inline int _write_trylock(rwlock_t *lock) return 0; } + check_lock(&lock->lock.debug, true); + /* * atomic_cmpxchg() is a full barrier so no need for an * arch_lock_acquire_barrier(). @@ -328,6 +340,8 @@ static inline void _percpu_read_lock(percpu_rwlock_t **per_cpudata, /* Drop the read lock because we don't need it anymore. */ read_unlock(&percpu_rwlock->rwlock); } + else + check_lock(&percpu_rwlock->rwlock.lock.debug, false); } static inline void _percpu_read_unlock(percpu_rwlock_t **per_cpudata, diff --git a/xen/include/xen/spinlock.h b/xen/include/xen/spinlock.h index ca13b600a0..9fa4e600c1 100644 --- a/xen/include/xen/spinlock.h +++ b/xen/include/xen/spinlock.h @@ -21,11 +21,13 @@ union lock_debug { }; }; #define _LOCK_DEBUG { LOCK_DEBUG_INITVAL } +void check_lock(union lock_debug *debug, bool try); void spin_debug_enable(void); void spin_debug_disable(void); #else union lock_debug { }; #define _LOCK_DEBUG { } +#define check_lock(l, t) ((void)0) #define spin_debug_enable() ((void)0) #define spin_debug_disable() ((void)0) #endif
Checking whether a lock is consistently used regarding interrupts on or off is beneficial for rwlocks, too. So add check_lock() calls to rwlock functions. For this purpose make check_lock() globally accessible. Signed-off-by: Juergen Gross <jgross@suse.com> --- xen/common/spinlock.c | 3 +-- xen/include/xen/rwlock.h | 14 ++++++++++++++ xen/include/xen/spinlock.h | 2 ++ 3 files changed, 17 insertions(+), 2 deletions(-)