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authorEric Dumazet <edumazet@google.com>2017-03-01 14:28:39 -0800
committerDavid S. Miller <davem@davemloft.net>2017-03-01 20:55:57 -0800
commit13baa00ad01bb3a9f893e3a08cbc2d072fc0c15d (patch)
treeebcc0624dcccf6c25949f3e52c26a75f542bb7b8
parent540e2894f7905538740aaf122bd8e0548e1c34a4 (diff)
downloadlinux-13baa00ad01bb3a9f893e3a08cbc2d072fc0c15d.tar.gz
net: net_enable_timestamp() can be called from irq contexts
It is now very clear that silly TCP listeners might play with enabling/disabling timestamping while new children are added to their accept queue. Meaning net_enable_timestamp() can be called from BH context while current state of the static key is not enabled. Lets play safe and allow all contexts. The work queue is scheduled only under the problematic cases, which are the static key enable/disable transition, to not slow down critical paths. This extends and improves what we did in commit 5fa8bbda38c6 ("net: use a work queue to defer net_disable_timestamp() work") Fixes: b90e5794c5bd ("net: dont call jump_label_dec from irq context") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/core/dev.c35
1 files changed, 31 insertions, 4 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index e63bf61..8637b2b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1698,27 +1698,54 @@ EXPORT_SYMBOL_GPL(net_dec_egress_queue);
static struct static_key netstamp_needed __read_mostly;
#ifdef HAVE_JUMP_LABEL
static atomic_t netstamp_needed_deferred;
+static atomic_t netstamp_wanted;
static void netstamp_clear(struct work_struct *work)
{
int deferred = atomic_xchg(&netstamp_needed_deferred, 0);
+ int wanted;
- while (deferred--)
- static_key_slow_dec(&netstamp_needed);
+ wanted = atomic_add_return(deferred, &netstamp_wanted);
+ if (wanted > 0)
+ static_key_enable(&netstamp_needed);
+ else
+ static_key_disable(&netstamp_needed);
}
static DECLARE_WORK(netstamp_work, netstamp_clear);
#endif
void net_enable_timestamp(void)
{
+#ifdef HAVE_JUMP_LABEL
+ int wanted;
+
+ while (1) {
+ wanted = atomic_read(&netstamp_wanted);
+ if (wanted <= 0)
+ break;
+ if (atomic_cmpxchg(&netstamp_wanted, wanted, wanted + 1) == wanted)
+ return;
+ }
+ atomic_inc(&netstamp_needed_deferred);
+ schedule_work(&netstamp_work);
+#else
static_key_slow_inc(&netstamp_needed);
+#endif
}
EXPORT_SYMBOL(net_enable_timestamp);
void net_disable_timestamp(void)
{
#ifdef HAVE_JUMP_LABEL
- /* net_disable_timestamp() can be called from non process context */
- atomic_inc(&netstamp_needed_deferred);
+ int wanted;
+
+ while (1) {
+ wanted = atomic_read(&netstamp_wanted);
+ if (wanted <= 1)
+ break;
+ if (atomic_cmpxchg(&netstamp_wanted, wanted, wanted - 1) == wanted)
+ return;
+ }
+ atomic_dec(&netstamp_needed_deferred);
schedule_work(&netstamp_work);
#else
static_key_slow_dec(&netstamp_needed);