execve: improve interactivity with large arguments

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@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/exec.c b/fs/exec.c
index f1bb0d21d080de6f67d68fcda01be1bac8a20237..e8214175cbaaf51d1970b894ccf99ce663176766 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -420,6 +420,8 @@ static int copy_strings(int argc, char __user * __user * argv,
                while (len > 0) {
                        int offset, bytes_to_copy;
 
+                       cond_resched();
+
                        offset = pos % PAGE_SIZE;
                        if (offset == 0)
                                offset = PAGE_SIZE;