Subject: + ipcshm-make-shmctl_nolock-lockless.patch added to -mm tree
To: davidlohr.bueso@xxxxxx,manfred@xxxxxxxxxxxxxxxx,riel@xxxxxxxxxx,sedat.dilek@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 16 Jul 2013 15:51:48 -0700
The patch titled
Subject: ipc,shm: make shmctl_nolock lockless
has been added to the -mm tree. Its filename is
ipcshm-make-shmctl_nolock-lockless.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipcshm-make-shmctl_nolock-lockless.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipcshm-make-shmctl_nolock-lockless.patch
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------------------------------------------------------
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Subject: ipc,shm: make shmctl_nolock lockless
While the INFO cmd doesn't take the ipc lock, the STAT commands do acquire
it unnecessarily. We can do the permissions and security checks only
holding the rcu lock.
Signed-off-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/shm.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
diff -puN ipc/shm.c~ipcshm-make-shmctl_nolock-lockless ipc/shm.c
--- a/ipc/shm.c~ipcshm-make-shmctl_nolock-lockless
+++ a/ipc/shm.c
@@ -882,27 +882,31 @@ static int shmctl_nolock(struct ipc_name
struct shmid64_ds tbuf;
int result;
+ rcu_read_lock();
if (cmd == SHM_STAT) {
- shp = shm_lock(ns, shmid);
+ shp = shm_obtain_object(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
- goto out;
+ goto out_unlock;
}
result = shp->shm_perm.id;
} else {
- shp = shm_lock_check(ns, shmid);
+ shp = shm_obtain_object_check(ns, shmid);
if (IS_ERR(shp)) {
err = PTR_ERR(shp);
- goto out;
+ goto out_unlock;
}
result = 0;
}
+
err = -EACCES;
if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
goto out_unlock;
+
err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock;
+
memset(&tbuf, 0, sizeof(tbuf));
kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
tbuf.shm_segsz = shp->shm_segsz;
@@ -912,8 +916,9 @@ static int shmctl_nolock(struct ipc_name
tbuf.shm_cpid = shp->shm_cprid;
tbuf.shm_lpid = shp->shm_lprid;
tbuf.shm_nattch = shp->shm_nattch;
- shm_unlock(shp);
- if(copy_shmid_to_user (buf, &tbuf, version))
+ rcu_read_unlock();
+
+ if (copy_shmid_to_user (buf, &tbuf, version))
err = -EFAULT;
else
err = result;
@@ -924,7 +929,7 @@ static int shmctl_nolock(struct ipc_name
}
out_unlock:
- shm_unlock(shp);
+ rcu_read_unlock();
out:
return err;
}
_
Patches currently in -mm which might be from davidlohr.bueso@xxxxxx are
linux-next.patch
ipcshm-introduce-lockless-functions-to-obtain-the-ipc-object.patch
ipcshm-shorten-critical-region-in-shmctl_down.patch
ipc-drop-ipcctl_pre_down.patch
ipc-drop-ipcctl_pre_down-fix.patch
ipcshm-introduce-shmctl_nolock.patch
ipcshm-make-shmctl_nolock-lockless.patch
ipcshm-shorten-critical-region-for-shmctl.patch
ipcshm-cleanup-do_shmat-pasta.patch
ipcshm-shorten-critical-region-for-shmat.patch
ipc-rename-ids-rw_mutex.patch
ipcmsg-drop-msg_unlock.patch
ipc-document-general-ipc-locking-scheme.patch
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