Commit-ID: f0bab73cb539fb803c4d419951e8d28aa4964f8f Gitweb: http://git.kernel.org/tip/f0bab73cb539fb803c4d419951e8d28aa4964f8f Author: Waiman Long <Waiman.Long@xxxxxx> AuthorDate: Wed, 6 Aug 2014 13:22:01 -0400 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 13 Aug 2014 10:33:34 +0200 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@xxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Scott J Norton <scott.norton@xxxxxx> Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1407345722-61615-2-git-send-email-Waiman.Long@xxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- include/linux/lockdep.h | 10 +++++++++- kernel/locking/lockdep.c | 6 ++++++ 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index f388481..b5a84b62 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 88d0d44..420ba68 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3597,6 +3597,12 @@ 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, -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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