linux-kernel - Re: [PATCH 1/5] sched: Convert thread_group_cputime() to use for_each

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Message-ID: <20140410161955.GG13658@twins.programming.kicks-ass.net>
Date:	Thu, 10 Apr 2014 18:19:55 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 1/5] sched: Convert thread_group_cputime() to use
 for_each_thread()

On Wed, Apr 09, 2014 at 09:49:57PM +0200, Peter Zijlstra wrote:
> Anyway, I'll look over the stuff tomorrow.

That patch was missing useful clues..

Also, I shot __for_each_thread in the head, it seemed useless.

---
 include/linux/sched.h | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7cb07fd26680..6f995bef45d3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2377,6 +2377,9 @@ extern bool current_is_single_threaded(void);
 /*
  * Careful: do_each_thread/while_each_thread is a double loop so
  *          'break' will not work as expected - use goto instead.
+ *
+ * Deprecated; use for_each_thread() instead; this has serious issues with
+ * g != current and RCU.
  */
 #define do_each_thread(g, t) \
 	for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do
@@ -2384,11 +2387,8 @@ extern bool current_is_single_threaded(void);
 #define while_each_thread(g, t) \
 	while ((t = next_thread(t)) != g)
 
-#define __for_each_thread(signal, t)	\
-	list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node)
-
 #define for_each_thread(p, t)		\
-	__for_each_thread((p)->signal, t)
+	list_for_each_entry_rcu(t, &(p)->signal->thread_head, thread_node)
 
 /* Careful: this is a double loop, 'break' won't work as expected. */
 #define for_each_process_thread(p, t)	\
@@ -2421,7 +2421,8 @@ bool same_thread_group(struct task_struct *p1, struct task_struct *p2)
 	return p1->signal == p2->signal;
 }
 
-static inline struct task_struct *next_thread(const struct task_struct *p)
+static inline __deprecated
+struct task_struct *next_thread(const struct task_struct *p)
 {
 	return list_entry_rcu(p->thread_group.next,
 			      struct task_struct, thread_group);
--
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