Commit 112a0e41 authored Jul 28, 2020 by Masami Hiramatsu Committed by Ingo Molnar Jul 28, 2020

kprobes: Remove unnecessary module_mutex locking from kprobe_optimizer()



Since we already lock both kprobe_mutex and text_mutex in the optimizer,
text will not be changed and the module unloading will be stopped
inside kprobes_module_callback().

The mutex_lock() has originally been introduced to avoid conflict with text modification,
at that point we didn't hold text_mutex.

But after:

  f1c6ece2 ("kprobes: Fix potential deadlock in kprobe_optimizer()")

We started holding the text_mutex and don't need the modules mutex anyway.

So remove the module_mutex locking.

[ mingo: Amended the changelog. ]

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Link: https://lore.kernel.org/r/20200728163400.e00b09c594763349f99ce6cb@kernel.org

parent e89d4ca1

kernel/kprobes.c

+0 −3

Original line number	Diff line number	Diff line
		@@ -598,8 +598,6 @@ static void kprobe_optimizer(struct work_struct *work)
		mutex_lock(&kprobe_mutex);
		cpus_read_lock();
		mutex_lock(&text_mutex);
		/* Lock modules while optimizing kprobes */
		mutex_lock(&module_mutex);

		/*
		* Step 1: Unoptimize kprobes and collect cleaned (unused and disarmed)
		@@ -624,7 +622,6 @@ static void kprobe_optimizer(struct work_struct *work)
		/* Step 4: Free cleaned kprobes after quiesence period */
		do_free_cleaned_kprobes();

		mutex_unlock(&module_mutex);
		mutex_unlock(&text_mutex);
		cpus_read_unlock();

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