linux-kernel - [16/17] execve: improve interactivity with large arguments

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Message-Id: <20101022184033.920409577@clark.site>
Date:	Fri, 22 Oct 2010 11:39:41 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Roland McGrath <roland@...hat.com>,
	Chuck Ebbert <cebbert@...hat.com>
Subject: [16/17] execve: improve interactivity with large arguments

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Roland McGrath <roland@...hat.com>

commit 7993bc1f4663c0db67bb8f0d98e6678145b387cd upstream.

This adds a preemption point during the copying of the argument and
environment strings for execve, in copy_strings().  There is already
a preemption point in the count() loop, so this doesn't add any new
points in the abstract sense.

When the total argument+environment strings are very large, the time
spent copying them can be much more than a normal user time slice.
So this change improves the interactivity of the rest of the system
when one process is doing an execve with very large arguments.

Signed-off-by: Roland McGrath <roland@...hat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Chuck Ebbert <cebbert@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/exec.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/exec.c
+++ b/fs/exec.c
@@ -436,6 +436,8 @@ static int copy_strings(int argc, char _
 		while (len > 0) {
 			int offset, bytes_to_copy;
 
+			cond_resched();
+
 			offset = pos % PAGE_SIZE;
 			if (offset == 0)
 				offset = PAGE_SIZE;


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