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 55cfaa3c 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 1e50df39 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>
parent
22bacca4
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