linux.git/ipc/msg.c, branch v3.11-rc2

ipc: remove unused functions

2013-07-09T17:33:27+00:00

We can now drop the msg_lock and msg_lock_check functions along with a
bogus comment introduced previously in semctl_down.

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,msg: shorten critical region in msgrcv

2013-07-09T17:33:27+00:00

do_msgrcv() is the last msg queue function that abuses the ipc lock Take
it only when needed when actually updating msq.

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Tested-by: Sedat Dilek 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,msg: shorten critical region in msgsnd

2013-07-09T17:33:27+00:00

do_msgsnd() is another function that does too many things with the ipc
object lock acquired.  Take it only when needed when actually updating
msq.

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,msg: make msgctl_nolock lockless

2013-07-09T17:33:27+00:00

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.

This function now mimics semctl_nolock().

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,msg: introduce lockless functions to obtain the ipc object

2013-07-09T17:33:27+00:00

Add msq_obtain_object() and msq_obtain_object_check(), which will allow
us to get the ipc object without acquiring the lock.  Just as with
semaphores, these functions are basically wrappers around
ipc_obtain_object*().

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,msg: introduce msgctl_nolock

2013-07-09T17:33:27+00:00

Similar to semctl, when calling msgctl, the *_INFO and *_STAT commands
can be performed without acquiring the ipc object.

Add a msgctl_nolock() function and move the logic of *_INFO and *_STAT
out of msgctl().  This change still takes the lock and it will be
properly lockless in the next patch

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc,msg: shorten critical region in msgctl_down

2013-07-09T17:33:27+00:00

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 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc: move locking out of ipcctl_pre_down_nolock

2013-07-09T17:33:27+00:00

This function currently acquires both the rw_mutex and the rcu lock on
successful lookups, leaving the callers to explicitly unlock them,
creating another two level locking situation.

Make the callers (including those that still use ipcctl_pre_down())
explicitly lock and unlock the rwsem and rcu lock.

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc: close open coded spin lock calls

2013-07-09T17:33:27+00:00

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ipc: move rcu lock out of ipc_addid

2013-07-09T17:33:26+00:00

This patchset continues the work that began in the sysv ipc semaphore
scaling series, see

  https://lkml.org/lkml/2013/3/20/546

Just like semaphores used to be, sysv shared memory and msg queues also
abuse the ipc lock, unnecessarily holding it for operations such as
permission and security checks.

This patchset mostly deals with mqueues, and while shared mem can be
done in a very similar way, I want to get these patches out in the open
first.  It also does some pending cleanups, mostly focused on the two
level locking we have in ipc code, taking care of ipc_addid() and
ipcctl_pre_down_nolock() - yes there are still functions that need to be
updated as well.

This patch:

Make all callers explicitly take and release the RCU read lock.

This addresses the two level locking seen in newary(), newseg() and
newqueue().  For the last two, explicitly unlock the ipc object and the
rcu lock, instead of calling the custom shm_unlock and msg_unlock
functions.  The next patch will deal with the open coded locking for
->perm.lock

Signed-off-by: Davidlohr Bueso 
Cc: Andi Kleen 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds