[34-longterm 216/260] execve: improve interactivity with large arguments

From: Paul Gortmaker
Date: Sun Jan 02 2011 - 02:33:08 EST

From: Roland McGrath <roland@xxxxxxxxxx>

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@xxxxxxxxxx>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
fs/exec.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index b884fde..b187ab0 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -419,6 +419,8 @@ 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;

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