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Commit 15724ecb7e9bab35fc694c666ad563adba820cc3

Authored by Davidlohr Bueso
Committed by Linus Torvalds
1 parent 7b4cc5d841
Exists in smarc-imx_3.14.28_1.0.0_ga and in 1 other branch imx_3.14.28_1.0.0_ga

ipc,msg: shorten critical region in msgctl_down 

Instead of holding the ipc lock for the entire function, use the
ipcctl_pre_down_nolock and only acquire the lock for specific commands:
RMID and SET.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 1 changed file with 7 additions and 5 deletions Side-by-side Diff

... ... @@ -410,11 +410,10 @@
410 410 down_write(&msg_ids(ns).rw_mutex);
411 411 rcu_read_lock();
412 412  
413   - ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
414   - &msqid64.msg_perm, msqid64.msg_qbytes);
  413 + ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
  414 + &msqid64.msg_perm, msqid64.msg_qbytes);
415 415 if (IS_ERR(ipcp)) {
416 416 err = PTR_ERR(ipcp);
417   - /* the ipc lock is not held upon failure */
418 417 goto out_unlock1;
419 418 }
420 419  
421 420  
... ... @@ -422,10 +421,11 @@
422 421  
423 422 err = security_msg_queue_msgctl(msq, cmd);
424 423 if (err)
425   - goto out_unlock0;
  424 + goto out_unlock1;
426 425  
427 426 switch (cmd) {
428 427 case IPC_RMID:
  428 + ipc_lock_object(&msq->q_perm);
429 429 /* freeque unlocks the ipc object and rcu */
430 430 freeque(ns, ipcp);
431 431 goto out_up;
432 432  
... ... @@ -433,9 +433,10 @@
433 433 if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
434 434 !capable(CAP_SYS_RESOURCE)) {
435 435 err = -EPERM;
436   - goto out_unlock0;
  436 + goto out_unlock1;
437 437 }
438 438  
  439 + ipc_lock_object(&msq->q_perm);
439 440 err = ipc_update_perm(&msqid64.msg_perm, ipcp);
440 441 if (err)
441 442 goto out_unlock0;
... ... @@ -454,6 +455,7 @@
454 455 break;
455 456 default:
456 457 err = -EINVAL;
  458 + goto out_unlock1;
457 459 }
458 460  
459 461 out_unlock0: