xfrm: avoid spinlock in get_acqseq() used by xfrm user
jamal [Tue, 16 Feb 2010 02:01:22 +0000 (02:01 +0000)]
Eric's version fixed it for pfkey. This one is for xfrm user.
I thought about amortizing those two get_acqseq()s but it seems
reasonable to have two of these sequence spaces for the two different
interfaces.

cheers,
jamal
commit d5168d5addbc999c94aacda8f28a4a173756a72b
Author: Jamal Hadi Salim <hadi@cyberus.ca>
Date:   Tue Feb 16 06:51:22 2010 -0500

    xfrm: avoid spinlock in get_acqseq() used by xfrm user

    This is in the same spirit as commit 28aecb9d7728dc26bf03ce7925fe622023a83a2a
    by Eric Dumazet.
    Use atomic_inc_return() in get_acqseq() to avoid taking a spinlock

Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_state.c

index f50ee9b..96f2088 100644 (file)
@@ -1462,12 +1462,12 @@ EXPORT_SYMBOL(xfrm_find_acq_byseq);
 u32 xfrm_get_acqseq(void)
 {
        u32 res;
-       static u32 acqseq;
-       static DEFINE_SPINLOCK(acqseq_lock);
+       static atomic_t acqseq;
+
+       do {
+               res = atomic_inc_return(&acqseq);
+       } while (!res);
 
-       spin_lock_bh(&acqseq_lock);
-       res = (++acqseq ? : ++acqseq);
-       spin_unlock_bh(&acqseq_lock);
        return res;
 }
 EXPORT_SYMBOL(xfrm_get_acqseq);