From: Steven Rostedt <srost...@redhat.com> Currently module_mutex is taken before kprobe_mutex, but this can cause issues when we have kprobes register ftrace, as the ftrace mutex is taken before enabling a tracepoint, which currently takes the module mutex.
If module_mutex is taken before kprobe_mutex, then we can not have kprobes use the ftrace infrastructure. There seems to be no reason that the kprobe_mutex can't be taken before the module_mutex. Running lockdep shows that it is safe among the kernels I've run. Link: http://lkml.kernel.org/r/20120605102814.27845.21047.stgit@localhost.localdomain Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@redhat.com> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: Ananth N Mavinakayanahalli <ana...@in.ibm.com> Cc: "Frank Ch. Eigler" <f...@redhat.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Frederic Weisbecker <fweis...@gmail.com> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Signed-off-by: Steven Rostedt <rost...@goodmis.org> --- kernel/kprobes.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index c62b854..7a8a122 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -561,9 +561,9 @@ static __kprobes void kprobe_optimizer(struct work_struct *work) { LIST_HEAD(free_list); + mutex_lock(&kprobe_mutex); /* Lock modules while optimizing kprobes */ mutex_lock(&module_mutex); - mutex_lock(&kprobe_mutex); /* * Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed) @@ -586,8 +586,8 @@ static __kprobes void kprobe_optimizer(struct work_struct *work) /* Step 4: Free cleaned kprobes after quiesence period */ do_free_cleaned_kprobes(&free_list); - mutex_unlock(&kprobe_mutex); mutex_unlock(&module_mutex); + mutex_unlock(&kprobe_mutex); /* Step 5: Kick optimizer again if needed */ if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) -- 1.7.10.4
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