AcoSail/kernel_optimize_test
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pppoatm: optimise PPP channel wakeups after sock_owned_by_user()

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We don't need to schedule the wakeup tasklet on *every* unlock; only if we
actually blocked the channel in the first place.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: Krzysztof Mazur <krzysiek@podlesie.net>
This commit is contained in:
David Woodhouse 2012-11-28 10:15:05 +00:00
parent 9eba25268e
commit 5b4d72080f
1 changed files with 19 additions and 2 deletions
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21
net/atm/pppoatm.c
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@ -113,7 +113,17 @@ static void pppoatm_release_cb(struct atm_vcc *atmvcc)
{
struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
tasklet_schedule(&pvcc->wakeup_tasklet);
/*
* As in pppoatm_pop(), it's safe to clear the BLOCKED bit here because
* the wakeup *can't* race with pppoatm_send(). They both hold the PPP
* channel's ->downl lock. And the potential race with *setting* it,
* which leads to the double-check dance in pppoatm_may_send(), doesn't
* exist here. In the sock_owned_by_user() case in pppoatm_send(), we
* set the BLOCKED bit while the socket is still locked. We know that
* ->release_cb() can't be called until that's done.
*/
if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
tasklet_schedule(&pvcc->wakeup_tasklet);
if (pvcc->old_release_cb)
pvcc->old_release_cb(atmvcc);
}
@ -292,8 +302,15 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
vcc = ATM_SKB(skb)->vcc;
bh_lock_sock(sk_atm(vcc));
if (sock_owned_by_user(sk_atm(vcc)))
if (sock_owned_by_user(sk_atm(vcc))) {
/*
* Needs to happen (and be flushed, hence test_and_) before we unlock
* the socket. It needs to be seen by the time our ->release_cb gets
* called.
*/
test_and_set_bit(BLOCKED, &pvcc->blocked);
goto nospace;
}
if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
test_bit(ATM_VF_CLOSE, &vcc->flags) ||
!test_bit(ATM_VF_READY, &vcc->flags)) {