Commit 6932689e authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

livepatch: Replace synchronize_sched() with synchronize_rcu() 



Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu().  This commit therefore makes this change,
even though it is but a comment.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 2af3024c

kernel/livepatch/patch.c

+2 −2
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ static void notrace klp_ftrace_handler(unsigned long ip, 
	ops = container_of(fops, struct klp_ops, fops);



	/*

	 * A variant of synchronize_sched() is used to allow patching functions

	 * A variant of synchronize_rcu() is used to allow patching functions

	 * where RCU is not watching, see klp_synchronize_transition().

	 */

	preempt_disable_notrace();
@@ -72,7 +72,7 @@ static void notrace klp_ftrace_handler(unsigned long ip, 
	/*

	 * func should never be NULL because preemption should be disabled here

	 * and unregister_ftrace_function() does the equivalent of a

	 * synchronize_sched() before the func_stack removal.

	 * synchronize_rcu() before the func_stack removal.

	 */

	if (WARN_ON_ONCE(!func))

		goto unlock;

kernel/livepatch/transition.c

+2 −2
Original line number Diff line number Diff line
@@ -52,7 +52,7 @@ static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); 


/*

 * This function is just a stub to implement a hard force

 * of synchronize_sched(). This requires synchronizing

 * of synchronize_rcu(). This requires synchronizing

 * tasks even in userspace and idle.

 */

static void klp_sync(struct work_struct *work)
@@ -175,7 +175,7 @@ void klp_cancel_transition(void) 
void klp_update_patch_state(struct task_struct *task)

{

	/*

	 * A variant of synchronize_sched() is used to allow patching functions

	 * A variant of synchronize_rcu() is used to allow patching functions

	 * where RCU is not watching, see klp_synchronize_transition().

	 */

	preempt_disable_notrace();

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