Messages in this thread Patch in this message | | | Date | Tue, 29 Apr 2008 18:28:32 +0530 | From | Gautham R Shenoy <> | Subject | [PATCH 2/8] lockdep: reader-in-writer recursion |
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Subject: lockdep: reader-in-writer recursion
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Create a read mode that allows for reader-in-writer recursion
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> ---
include/linux/lockdep.h | 1 + kernel/lockdep.c | 9 ++++++++- 2 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 4c4d236..36e254f 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -291,6 +291,7 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name, * 0: exclusive (write) acquire * 1: read-acquire (no recursion allowed) * 2: read-acquire with same-instance recursion allowed + * 3: 2 + reader in writer recursion * * Values for check: * diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 94b0f4f..3859259 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -1280,6 +1280,13 @@ check_deadlock(struct task_struct *curr, struct held_lock *next, */ if ((read == 2) && prev->read) return 2; + /* + * Allow read-after-write recursion of the same + * lock class (i.e. write_lock(lock)+read_lock(lock)): + */ + if (read == 3) + return 2; + return print_deadlock_bug(curr, prev, next); } return 1; @@ -1559,7 +1566,7 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, * If we are the first recursive read, don't jump over our * dependency. */ - if (hlock->read == 2 && ret != 2) + if (hlock->read >= 2 && ret != 2) hlock->read = 1; /* * Add dependency only if this lock is not the head -- Thanks and Regards gautham
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