linux-kernel - [tip:sched/core] sched/preempt: Fix preempt notifiers documentation about hlist

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Message-ID: <tip-d84525a845cc2617d638349f8756a9fec9ac8113@git.kernel.org>
Date:	Fri, 19 Jun 2015 11:00:57 -0700
From:	tip-bot for Mathieu Desnoyers <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	peterz@...radead.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, tglx@...utronix.de, bp@...en8.de,
	mathieu.desnoyers@...icios.com, hpa@...or.com,
	linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: [tip:sched/core] sched/preempt:
  Fix preempt notifiers documentation about hlist_del()
  within unsafe iteration

Commit-ID:  d84525a845cc2617d638349f8756a9fec9ac8113
Gitweb:     http://git.kernel.org/tip/d84525a845cc2617d638349f8756a9fec9ac8113
Author:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
AuthorDate: Sun, 17 May 2015 12:53:10 -0400
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 19 Jun 2015 10:06:44 +0200

sched/preempt: Fix preempt notifiers documentation about hlist_del() within unsafe iteration

preempt_notifier_unregister() documents:

  "This is safe to call from within a preemption notifier."

However, both fire_sched_in_preempt_notifiers() and
fire_sched_out_preempt_notifiers() are using hlist_for_each_entry(),
which is not safe against entry removal during iteration.

Inspection of the KVM code does not reveal any use of
preempt_notifier_unregister() within the preempt notifiers.

Therefore, fix the comment.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1431881590-1456-1-git-send-email-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index af0a5a6..bdb7aa6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2165,7 +2165,7 @@ EXPORT_SYMBOL_GPL(preempt_notifier_register);
  * preempt_notifier_unregister - no longer interested in preemption notifications
  * @notifier: notifier struct to unregister
  *
- * This is safe to call from within a preemption notifier.
+ * This is *not* safe to call from within a preemption notifier.
  */
 void preempt_notifier_unregister(struct preempt_notifier *notifier)
 {
--
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