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kprobes: Inverse taking of module_mutex with kprobe_mutex

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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/[email protected]

Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: "Frank Ch. Eigler" <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
This commit is contained in:
Steven Rostedt 2012-06-05 19:28:14 +09:00 • committed by Steven Rostedt
commit 72ef3794c5
1 changed files with 2 additions and 2 deletions
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4
kernel/kprobes.c
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@ -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))