Re: [1/2] [NET] link_watch: Move link watch list into net_device
From: David Miller <davem@davemloft.net>
Date: 2007-05-10 22:26:05
Also in:
lkml, netdev
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Jeremy Fitzhardinge <redacted> Date: Thu, 10 May 2007 15:22:17 -0700
Andrew Morton wrote:quoted
Five minutes after boot is when jiffies wraps. Are you sure it's a list-screwup rather than a jiffy-wrap screwup?Hm, its suggestive, isn't it? Apparently they've already fixed this in the sekret networking clubhouse, so I'll need to track it down.
I'm not so certain now that we know it's the jiffies wrap point :-)
The fixes in question are attached below and they were posted and
discussed on netdev:
--------------------
commit fe47cdba83b3041e4ac1aa1418431020a4afe1e0
Author: Herbert Xu [off-list ref]
Date: Tue May 8 23:22:43 2007 -0700
[NET] link_watch: Eliminate potential delay on wrap-around
When the jiffies wrap around or when the system boots up for the first
time, down events can be delayed indefinitely since we no longer
update linkwatch_nextevent when only urgent events are processed.
This patch fixes this by setting linkwatch_nextevent when a
wrap-around occurs.
Signed-off-by: Herbert Xu [off-list ref]
Signed-off-by: David S. Miller [off-list ref]
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index b5f4579..4674ae5 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c@@ -101,8 +101,10 @@ static void linkwatch_schedule_work(unsigned long delay) return; /* If we wrap around we'll delay it by at most HZ. */ - if (delay > HZ) + if (delay > HZ) { + linkwatch_nextevent = jiffies; delay = 0; + } schedule_delayed_work(&linkwatch_work, delay); } --------------------
commit 4cba637dbb9a13706494a1c85174c8e736914010
Author: Herbert Xu [off-list ref]
Date: Wed May 9 00:17:30 2007 -0700
[NET] link_watch: Always schedule urgent events
Urgent events may be delayed if we already have a non-urgent event
queued for that device. This patch changes this by making sure that
an urgent event is always looked at immediately.
I've replaced the LW_RUNNING flag by LW_URGENT since whether work
is scheduled is already kept track by the work queue system.
The only complication is that we have to provide some exclusion for
the setting linkwatch_nextevent which is available in the actual
work function.
Signed-off-by: Herbert Xu [off-list ref]
Signed-off-by: David S. Miller [off-list ref]
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 4674ae5..a5e372b 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c@@ -26,7 +26,7 @@ enum lw_bits { - LW_RUNNING = 0, + LW_URGENT = 0, }; static unsigned long linkwatch_flags;
@@ -95,18 +95,41 @@ static void linkwatch_add_event(struct net_device *dev) } -static void linkwatch_schedule_work(unsigned long delay) +static void linkwatch_schedule_work(int urgent) { - if (test_and_set_bit(LW_RUNNING, &linkwatch_flags)) + unsigned long delay = linkwatch_nextevent - jiffies; + + if (test_bit(LW_URGENT, &linkwatch_flags)) return; - /* If we wrap around we'll delay it by at most HZ. */ - if (delay > HZ) { - linkwatch_nextevent = jiffies; + /* Minimise down-time: drop delay for up event. */ + if (urgent) { + if (test_and_set_bit(LW_URGENT, &linkwatch_flags)) + return; delay = 0; } - schedule_delayed_work(&linkwatch_work, delay); + /* If we wrap around we'll delay it by at most HZ. */ + if (delay > HZ) + delay = 0; + + /* + * This is true if we've scheduled it immeditately or if we don't + * need an immediate execution and it's already pending. + */ + if (schedule_delayed_work(&linkwatch_work, delay) == !delay) + return; + + /* Don't bother if there is nothing urgent. */ + if (!test_bit(LW_URGENT, &linkwatch_flags)) + return; + + /* It's already running which is good enough. */ + if (!cancel_delayed_work(&linkwatch_work)) + return; + + /* Otherwise we reschedule it again for immediate exection. */ + schedule_delayed_work(&linkwatch_work, 0); }
@@ -123,7 +146,11 @@ static void __linkwatch_run_queue(int urgent_only) */ if (!urgent_only) linkwatch_nextevent = jiffies + HZ; - clear_bit(LW_RUNNING, &linkwatch_flags); + /* Limit wrap-around effect on delay. */ + else if (time_after(linkwatch_nextevent, jiffies + HZ)) + linkwatch_nextevent = jiffies; + + clear_bit(LW_URGENT, &linkwatch_flags); spin_lock_irq(&lweventlist_lock); next = lweventlist;
@@ -166,7 +193,7 @@ static void __linkwatch_run_queue(int urgent_only) } if (lweventlist) - linkwatch_schedule_work(linkwatch_nextevent - jiffies); + linkwatch_schedule_work(0); }
@@ -187,21 +214,16 @@ static void linkwatch_event(struct work_struct *dummy) void linkwatch_fire_event(struct net_device *dev) { - if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) { - unsigned long delay; + int urgent = linkwatch_urgent_event(dev); + if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) { dev_hold(dev); linkwatch_add_event(dev); + } else if (!urgent) + return; - delay = linkwatch_nextevent - jiffies; - - /* Minimise down-time: drop delay for up event. */ - if (linkwatch_urgent_event(dev)) - delay = 0; - - linkwatch_schedule_work(delay); - } + linkwatch_schedule_work(urgent); } EXPORT_SYMBOL(linkwatch_fire_event); --------------------