David Miller a écrit :
From: Joonwoo Park <[EMAIL PROTECTED]>
Date: Tue, 22 Jan 2008 00:08:57 +0900
The rt_run_flush() can be stucked if it was called while netdev is on the
high load.
It's possible when pushing rtable to rt_hash is faster than pulling
from it.
The commands 'ifconfig up or ifconfig mtu' and netif_carrier_on() can
introduce soft lockup like this:
[ 363.528001] BUG: soft lockup - CPU#0 stuck for 11s! [events/0:9]
[ 363.531492]
[ 363.535027] Pid: 9, comm: events/0 Not tainted (2.6.24-rc8 #14)
[ 363.538837] EIP: 0060:[<c4086a39>] EFLAGS: 00000286 CPU: 0
[ 363.542762] EIP is at kfree+0xa9/0xf0
...
[ 363.660815] [<c42fb0fd>] skb_release_data+0x5d/0x90
[ 363.666989] [<c42fb7dc>] skb_release_all+0x5c/0xd0
[ 363.673207] [<c42faf8b>] __kfree_skb+0xb/0x90
[ 363.679474] [<c42fb029>] kfree_skb+0x19/0x40
[ 363.685811] [<c4322d87>] ip_rcv+0x27/0x290
[ 363.692223] [<c4300ae5>] netif_receive_skb+0x255/0x320
[ 363.698759] [<f88465aa>] e1000_clean_rx_irq+0x14a/0x4f0 [e1000]
[ 363.705456] [<f88437c2>] e1000_clean+0x62/0x270 [e1000]
[ 363.712217] [<c43031ee>] net_rx_action+0x16e/0x220
[ 363.719065] [<c40346d7>] __do_softirq+0x87/0x100
[ 363.726001] [<c40347a7>] do_softirq+0x57/0x60
[ 363.732979] [<c4034b4e>] local_bh_enable_ip+0xae/0x100
[ 363.740094] [<c43e73f5>] _spin_unlock_bh+0x25/0x30
[ 363.747283] [<c431ec88>] rt_run_flush+0xc8/0xe0
[ 363.754566] [<c4320c76>] rt_cache_flush+0xd6/0xe0
[ 363.761917] [<c4350269>] fib_netdev_event+0x89/0xa0
[ 363.769361] [<c4047d67>] notifier_call_chain+0x37/0x80
...
This patch makes rt_run_flush() to run with softirq is disabled.
Signed-off-by: Joonwoo Park <[EMAIL PROTECTED]>
I agree with the analysis of the problem, however not the solution.
This will absolutely kill software interrupt latency.
In fact, we have moved much of the flush work into a workqueue in
net-2.6.25 because of how important that is
We need to find some other way to solve this.
Eric, any ideas?
Hum... 2.6.25 is certainly better in this aspect, but I remember we left
something to finish :)
We currently can have a worker doing the automatic flush every 600 seconds,
and another task doing a rt_cache_flush(...)
On very loaded machines (DDOS), routes might be added faster than deleted.
Also, each change in routes must invalidate rtcache, and/but full scan of this
cache is way too expensive (huge amount of MBytes must me read/written)
One possibility is to use a genid marker so that each entry can be thrown away
if its genid is different than the global one.
rt_cache_flush(-1) or rt_secret_build() would just have to increment the
global genid.
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