Messages in this thread Patch in this message | | | Subject | [PATCH v3 8/7] pppoatm: fix missing wakeup in pppoatm_send() | From | David Woodhouse <> | Date | Wed, 07 Nov 2012 12:52:14 +0000 |
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Now that we can return zero from pppoatm_send() for reasons *other* than the queue being full, that means we can't depend on a subsequent call to pppoatm_pop() waking the queue, and we might leave it stalled indefinitely.
Fix this by immediately scheduling the wakeup tasklet. As documented already elsewhere, the PPP channel's ->downl lock protects against the wakeup happening too soon and effectively being missed.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> ---- Untested. With this sorted, Acked-By: David Woodhouse <David.Woodhouse@intel.com< to the other seven. Thanks.
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c index 7507c20..56ad541 100644 --- a/net/atm/pppoatm.c +++ b/net/atm/pppoatm.c @@ -283,11 +283,11 @@ 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))) - goto nospace; + goto nospace_sched_wakeup; if (test_bit(ATM_VF_RELEASED, &vcc->flags) - || test_bit(ATM_VF_CLOSE, &vcc->flags) - || !test_bit(ATM_VF_READY, &vcc->flags)) - goto nospace; + || test_bit(ATM_VF_CLOSE, &vcc->flags) + || !test_bit(ATM_VF_READY, &vcc->flags)) + goto nospace_sched_wakeup; switch (pvcc->encaps) { /* LLC encapsulation needed */ case e_llc: @@ -328,7 +328,17 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) ? DROP_PACKET : 1; bh_unlock_sock(sk_atm(vcc)); return ret; -nospace: + nospace_sched_wakeup: + /* If we're returning zero for reasons *other* than the queue + * being full, then we need to ensure that a wakeup will + * happen and not just leave the channel stalled for ever. + * Just schedule the wakeup tasklet directly. As observed in + * pppoatm_pop(), it'll take the channel's ->downl lock which + * is also held by our caller, so it can't happen "too soon" + * and cause us to effectively miss a wakeup. + */ + tasklet_schedule(&pvcc->wakeup_tasklet); + nospace: bh_unlock_sock(sk_atm(vcc)); /* * We don't have space to send this SKB now, but we might have -- David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation
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