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Commit a879bf582dfb3a79d30d76ca3af2ae8a0f39010c

Authored by Greg Thelen
Committed by Linus Torvalds
1 parent 22bacca48a
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

mm: grab rcu read lock in move_pages() 

The move_pages() usage of find_task_by_vpid() requires rcu_read_lock() to
prevent free_pid() from reclaiming the pid.

Without this patch, RCU warnings are printed in v2.6.38-rc4 move_pages()
with:

  CONFIG_LOCKUP_DETECTOR=y
  CONFIG_PREEMPT=y
  CONFIG_LOCKDEP=y
  CONFIG_PROVE_LOCKING=y
  CONFIG_PROVE_RCU=y

Previously, migrate_pages() went through a similar transformation
replacing usage of tasklist_lock with rcu read lock:

  commit 55cfaa3cbdd29c4919ecb5fb8965c310f357e48c
  Author: Zeng Zhaoming <zengzm.kernel@gmail.com>
  Date:   Thu Dec 2 14:31:13 2010 -0800

      mm/mempolicy.c: add rcu read lock to protect pid structure

  commit 1e50df39f6e2c3a4a3394df62baa8a213df16c54
  Author: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
  Date:   Thu Jan 13 15:46:14 2011 -0800

      mempolicy: remove tasklist_lock from migrate_pages

Signed-off-by: Greg Thelen <gthelen@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Zeng Zhaoming <zengzm.kernel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 3 additions and 3 deletions Side-by-side Diff

... ... @@ -1287,14 +1287,14 @@
1287 1287 return -EPERM;
1288 1288  
1289 1289 /* Find the mm_struct */
1290   - read_lock(&tasklist_lock);
  1290 + rcu_read_lock();
1291 1291 task = pid ? find_task_by_vpid(pid) : current;
1292 1292 if (!task) {
1293   - read_unlock(&tasklist_lock);
  1293 + rcu_read_unlock();
1294 1294 return -ESRCH;
1295 1295 }
1296 1296 mm = get_task_mm(task);
1297   - read_unlock(&tasklist_lock);
  1297 + rcu_read_unlock();
1298 1298  
1299 1299 if (!mm)
1300 1300 return -EINVAL;