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    Subject[34-longterm 216/260] execve: improve interactivity with large arguments
    Date
    From: Roland McGrath <roland@redhat.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@redhat.com>
    Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    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;
    --
    1.7.3.3


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