Messages in this thread Patch in this message | | | Date | Fri, 5 Aug 2005 22:04:48 +0200 | From | Ingo Molnar <> | Subject | Re: [patch] preempt-trace.patch (mono preempt-trace) |
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* Dominik Karall <dominik.karall@gmx.net> wrote:
> With FRAME_POINTERS enabled: > > BUG: mono[3193] exited with nonzero preempt_count 1! > --------------------------- > | preempt count: 00000001 ] > | 1 level deep critical section nesting: > ---------------------------------------- > .. [<ffffffff80400a46>] .... _spin_lock+0x16/0x80 > .....[<ffffffff801ed30c>] .. ( <= sys_semtimedop+0x28c/0x7c0)
thanks. It seems semundo->lock somehow leaked. One possibility would be of semundo->refcount going from 2 to 1 while another thread has it locked. I dont see what prevents this scenario from happening. To test this theory, could you apply the patch below, which will do semundo locking not conditional on the refcount - does it fix the bug?
Ingo
ipc/sem.c | 10 +++------- 1 files changed, 3 insertions(+), 7 deletions(-)
Index: linux-preempt-trace/ipc/sem.c =================================================================== --- linux-preempt-trace.orig/ipc/sem.c +++ linux-preempt-trace/ipc/sem.c @@ -895,7 +895,7 @@ static inline void lock_semundo(void) struct sem_undo_list *undo_list; undo_list = current->sysvsem.undo_list; - if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1)) + if (undo_list) spin_lock(&undo_list->lock); } @@ -915,7 +915,7 @@ static inline void unlock_semundo(void) struct sem_undo_list *undo_list; undo_list = current->sysvsem.undo_list; - if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1)) + if (undo_list) spin_unlock(&undo_list->lock); } @@ -943,9 +943,7 @@ static inline int get_undo_list(struct s if (undo_list == NULL) return -ENOMEM; memset(undo_list, 0, size); - /* don't initialize unodhd->lock here. It's done - * in copy_semundo() instead. - */ + spin_lock_init(&undo_list->lock); atomic_set(&undo_list->refcnt, 1); current->sysvsem.undo_list = undo_list; } @@ -1231,8 +1229,6 @@ int copy_semundo(unsigned long clone_fla error = get_undo_list(&undo_list); if (error) return error; - if (atomic_read(&undo_list->refcnt) == 1) - spin_lock_init(&undo_list->lock); atomic_inc(&undo_list->refcnt); tsk->sysvsem.undo_list = undo_list; } else - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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