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Date: Tue, 29 Jul 2014 14:53:18 -0400 From: Waiman Long <Waiman.Long@...com> To: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Maarten Lankhorst <maarten.lankhorst@...onical.com>, Rik van Riel <riel@...hat.com> Cc: linux-kernel@...r.kernel.org, Scott J Norton <scott.norton@...com>, Fengguang Wu <fengguang.wu@...el.com>, Waiman Long <Waiman.Long@...com>, Peter Zijlstra <peterz@...radead.org> Subject: [PATCH 1/2 v6] locking/lockdep: Restrict the use of recursive read_lock() with qrwlock Unlike the original unfair rwlock implementation, queued rwlock will grant lock according to the chronological sequence of the lock requests except when the lock requester is in the interrupt context. Consequently, recursive read_lock calls will now hang the process if there is a write_lock call somewhere in between the read_lock calls. This patch updates the lockdep implementation to look for recursive read_lock calls. A new read state (3) is used to mark those read_lock call that cannot be recursively called except in the interrupt context. The new read state does exhaust the 2 bits available in held_lock:read bit field. The addition of any new read state in the future may require a redesign of how all those bits are squeezed together in the held_lock structure. Signed-off-by: Waiman Long <Waiman.Long@...com> Signed-off-by: Peter Zijlstra <peterz@...radead.org> --- include/linux/lockdep.h | 10 +++++++++- kernel/locking/lockdep.c | 6 ++++++ 2 files changed, 15 insertions(+), 1 deletions(-) diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 008388f..dadd6ba 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -478,16 +478,24 @@ static inline void print_irqtrace_events(struct task_struct *curr) * on the per lock-class debug mode: */ +/* + * Read states in the 2-bit held_lock:read field: + * 0: Exclusive lock + * 1: Shareable lock, cannot be recursively called + * 2: Shareable lock, can be recursively called + * 3: Shareable lock, cannot be recursively called except in interrupt context + */ #define lock_acquire_exclusive(l, s, t, n, i) lock_acquire(l, s, t, 0, 1, n, i) #define lock_acquire_shared(l, s, t, n, i) lock_acquire(l, s, t, 1, 1, n, i) #define lock_acquire_shared_recursive(l, s, t, n, i) lock_acquire(l, s, t, 2, 1, n, i) +#define lock_acquire_shared_irecursive(l, s, t, n, i) lock_acquire(l, s, t, 3, 1, n, i) #define spin_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) #define spin_acquire_nest(l, s, t, n, i) lock_acquire_exclusive(l, s, t, n, i) #define spin_release(l, n, i) lock_release(l, n, i) #define rwlock_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) -#define rwlock_acquire_read(l, s, t, i) lock_acquire_shared_recursive(l, s, t, NULL, i) +#define rwlock_acquire_read(l, s, t, i) lock_acquire_shared_irecursive(l, s, t, NULL, i) #define rwlock_release(l, n, i) lock_release(l, n, i) #define seqcount_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index d24e433..097f8ad 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3595,6 +3595,12 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass, raw_local_irq_save(flags); check_flags(flags); + /* + * An interrupt recursive read in interrupt context can be considered + * to be the same as a recursive read from checking perspective. + */ + if ((read == 3) && in_interrupt()) + read = 2; current->lockdep_recursion = 1; trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); __lock_acquire(lock, subclass, trylock, read, check, -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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