diff options
| author | David Woodhouse <David.Woodhouse@intel.com> | 2012-11-28 10:15:05 +0000 |
|---|---|---|
| committer | David Woodhouse <David.Woodhouse@intel.com> | 2012-12-02 00:05:20 +0000 |
| commit | 5b4d72080f49498d2390563aa90f5bc31785406c (patch) | |
| tree | 62da5867de0ff07672d07687adee6ce7bb9388af /net/atm | |
| parent | 9eba25268e5862571d53122065616c456fe1142a (diff) | |
| download | lwn-5b4d72080f49498d2390563aa90f5bc31785406c.tar.gz lwn-5b4d72080f49498d2390563aa90f5bc31785406c.zip | |
pppoatm: optimise PPP channel wakeups after sock_owned_by_user()
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>
Diffstat (limited to 'net/atm')
| -rw-r--r-- | net/atm/pppoatm.c | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c index 9fcda8c85e9a..8c93267ce969 100644 --- a/net/atm/pppoatm.c +++ b/net/atm/pppoatm.c @@ -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)) { |