linux-kernel - Re: ipc,sem: sysv semaphore scalability

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Date:	Tue, 26 Mar 2013 12:43:09 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dave Jones <davej@...hat.com>
Cc:	Rik van Riel <riel@...riel.com>, torvalds@...ux-foundation.org,
	davidlohr.bueso@...com, linux-kernel@...r.kernel.org,
	hhuang@...hat.com, jason.low2@...com, walken@...gle.com,
	lwoodman@...hat.com, chegu_vinod@...com,
	Peter Hurley <peter@...leysoftware.com>
Subject: Re: ipc,sem: sysv semaphore scalability

On Tue, 26 Mar 2013 15:28:52 -0400 Dave Jones <davej@...hat.com> wrote:

> On Thu, Mar 21, 2013 at 02:10:58PM -0700, Andrew Morton wrote:
> 
>  > Whichever way we go, we should get a wiggle on - this has been hanging
>  > around for too long.  Dave, do you have time to determine whether
>  > reverting 88b9e456b1649722673ff ("ipc: don't allocate a copy larger
>  > than max") fixes things up?
> 
> Ok, with that reverted it's been grinding away for a few hours without incident.
> Normally I see the oops within a minute or so.
> 

OK, thanks, I queued a revert:

From: Andrew Morton <akpm@...ux-foundation.org>
Subject: revert "ipc: don't allocate a copy larger than max"

Revert 88b9e456b164.  Dave has confirmed that this was causing oopses
during trinity testing.

Cc: Peter Hurley <peter@...leysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@...allels.com>
Reported-by: Dave Jones <davej@...hat.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 ipc/msg.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff -puN ipc/msg.c~revert-ipc-dont-allocate-a-copy-larger-than-max ipc/msg.c
--- a/ipc/msg.c~revert-ipc-dont-allocate-a-copy-larger-than-max
+++ a/ipc/msg.c
@@ -820,17 +820,15 @@ long do_msgrcv(int msqid, void __user *b
 	struct msg_msg *copy = NULL;
 	unsigned long copy_number = 0;
 
-	ns = current->nsproxy->ipc_ns;
-
 	if (msqid < 0 || (long) bufsz < 0)
 		return -EINVAL;
 	if (msgflg & MSG_COPY) {
-		copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax),
-				    msgflg, &msgtyp, &copy_number);
+		copy = prepare_copy(buf, bufsz, msgflg, &msgtyp, &copy_number);
 		if (IS_ERR(copy))
 			return PTR_ERR(copy);
 	}
 	mode = convert_mode(&msgtyp, msgflg);
+	ns = current->nsproxy->ipc_ns;
 
 	msq = msg_lock_check(ns, msqid);
 	if (IS_ERR(msq)) {
_

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