Messages in this thread Patch in this message | | | Date | Thu, 2 Feb 2006 11:53:54 +0530 | From | Ananth N Mavinakayanahalli <> | Subject | [PATCH] Kprobes: Fix deadlock in function-return probes |
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From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
When two function-return probes are inserted on kfree()[1] and the second on say, sys_link()[2], and later [2] is unregistered, we have a deadlock as kfree is called with the kretprobe_lock held and the function-return probe on kfree will also try to grab the same lock.
However, we can move the kfree() during unregistration to outside the spinlock as we are sure that no instances from the free list will be used after synchronized_sched() returns during the unregistration process. Thanks to Masami Hiramatsu for spotting this.
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> ---
kernel/kprobes.c | 2 +- 1 files changed, 1 insertion(+), 1 deletion(-)
Index: linux-2.6.16-rc1/kernel/kprobes.c =================================================================== --- linux-2.6.16-rc1.orig/kernel/kprobes.c +++ linux-2.6.16-rc1/kernel/kprobes.c @@ -631,12 +631,12 @@ void __kprobes unregister_kretprobe(stru unregister_kprobe(&rp->kp); /* No race here */ spin_lock_irqsave(&kretprobe_lock, flags); - free_rp_inst(rp); while ((ri = get_used_rp_inst(rp)) != NULL) { ri->rp = NULL; hlist_del(&ri->uflist); } spin_unlock_irqrestore(&kretprobe_lock, flags); + free_rp_inst(rp); } static int __init init_kprobes(void) - 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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