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authorOleg Nesterov <oleg@redhat.com>2012-03-23 18:02:47 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-23 19:58:41 -0400
commitd0bd587a80960d7ba7e0c8396e154028c9045c54 (patch)
tree3765f8eccdc5f982ba173a7a05d8981d573b9486 /kernel/kmod.c
parentb3449922502f5a161ee2b5022a33aec8472fbf18 (diff)
usermodehelper: implement UMH_KILLABLE
Implement UMH_KILLABLE, should be used along with UMH_WAIT_EXEC/PROC. The caller must ensure that subprocess_info->path/etc can not go away until call_usermodehelper_freeinfo(). call_usermodehelper_exec(UMH_KILLABLE) does wait_for_completion_killable. If it fails, it uses xchg(&sub_info->complete, NULL) to serialize with umh_complete() which does the same xhcg() to access sub_info->complete. If call_usermodehelper_exec wins, it can safely return. umh_complete() should get NULL and call call_usermodehelper_freeinfo(). Otherwise we know that umh_complete() was already called, in this case call_usermodehelper_exec() falls back to wait_for_completion() which should succeed "very soon". Note: UMH_NO_WAIT == -1 but it obviously should not be used with UMH_KILLABLE. We delay the neccessary cleanup to simplify the back porting. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Tejun Heo <tj@kernel.org> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/kmod.c')
-rw-r--r--kernel/kmod.c27
1 files changed, 25 insertions, 2 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 8ea25944ce33..f92f917c450c 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -201,7 +201,15 @@ EXPORT_SYMBOL(call_usermodehelper_freeinfo);
201 201
202static void umh_complete(struct subprocess_info *sub_info) 202static void umh_complete(struct subprocess_info *sub_info)
203{ 203{
204 complete(sub_info->complete); 204 struct completion *comp = xchg(&sub_info->complete, NULL);
205 /*
206 * See call_usermodehelper_exec(). If xchg() returns NULL
207 * we own sub_info, the UMH_KILLABLE caller has gone away.
208 */
209 if (comp)
210 complete(comp);
211 else
212 call_usermodehelper_freeinfo(sub_info);
205} 213}
206 214
207/* Keventd can't block, but this (a child) can. */ 215/* Keventd can't block, but this (a child) can. */
@@ -252,6 +260,9 @@ static void __call_usermodehelper(struct work_struct *work)
252 enum umh_wait wait = sub_info->wait; 260 enum umh_wait wait = sub_info->wait;
253 pid_t pid; 261 pid_t pid;
254 262
263 if (wait != UMH_NO_WAIT)
264 wait &= ~UMH_KILLABLE;
265
255 /* CLONE_VFORK: wait until the usermode helper has execve'd 266 /* CLONE_VFORK: wait until the usermode helper has execve'd
256 * successfully We need the data structures to stay around 267 * successfully We need the data structures to stay around
257 * until that is done. */ 268 * until that is done. */
@@ -461,9 +472,21 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info,
461 queue_work(khelper_wq, &sub_info->work); 472 queue_work(khelper_wq, &sub_info->work);
462 if (wait == UMH_NO_WAIT) /* task has freed sub_info */ 473 if (wait == UMH_NO_WAIT) /* task has freed sub_info */
463 goto unlock; 474 goto unlock;
475
476 if (wait & UMH_KILLABLE) {
477 retval = wait_for_completion_killable(&done);
478 if (!retval)
479 goto wait_done;
480
481 /* umh_complete() will see NULL and free sub_info */
482 if (xchg(&sub_info->complete, NULL))
483 goto unlock;
484 /* fallthrough, umh_complete() was already called */
485 }
486
464 wait_for_completion(&done); 487 wait_for_completion(&done);
488wait_done:
465 retval = sub_info->retval; 489 retval = sub_info->retval;
466
467out: 490out:
468 call_usermodehelper_freeinfo(sub_info); 491 call_usermodehelper_freeinfo(sub_info);
469unlock: 492unlock: