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authorEric Dumazet <eric.dumazet@gmail.com>2012-01-03 00:00:11 +0000
committerDavid S. Miller <davem@davemloft.net>2012-01-03 13:03:20 -0500
commitfa0f5aa74316c636427ac92dad0bc5714c34ca17 (patch)
tree64fcb6a7f4043cdaea4a13b730a1ca651190e314 /net/sched
parentd32ae76f2b776347051cf821ebe690602e38dfc7 (diff)
downloadblackbird-op-linux-fa0f5aa74316c636427ac92dad0bc5714c34ca17.tar.gz
blackbird-op-linux-fa0f5aa74316c636427ac92dad0bc5714c34ca17.zip
net_sched: qdisc_alloc_handle() can be too slow
When trying to allocate ~32768 qdiscs using autohandle mechanism, we can fill the space managed by kernel (handles in [8000-FFFF]:0000 range) But O(N^2) qdisc_alloc_handle() loops 0x10000 times instead of 0x8000 time tc add qdisc add dev eth0 parent 10:7fff pfifo limit 10 RTNETLINK answers: Cannot allocate memory real 1m54.826s user 0m0.000s sys 0m0.004s INFO: rcu_sched_state detected stall on CPU 0 (t=60000 jiffies) Half number of loops, and add a cond_resched() call. We hold rtnl at this point. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Dave Taht <dave.taht@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
-rw-r--r--net/sched/sch_api.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index dca6c1a576f7..3d8981fde301 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -618,20 +618,24 @@ void qdisc_class_hash_remove(struct Qdisc_class_hash *clhash,
}
EXPORT_SYMBOL(qdisc_class_hash_remove);
-/* Allocate an unique handle from space managed by kernel */
-
+/* Allocate an unique handle from space managed by kernel
+ * Possible range is [8000-FFFF]:0000 (0x8000 values)
+ */
static u32 qdisc_alloc_handle(struct net_device *dev)
{
- int i = 0x10000;
+ int i = 0x8000;
static u32 autohandle = TC_H_MAKE(0x80000000U, 0);
do {
autohandle += TC_H_MAKE(0x10000U, 0);
if (autohandle == TC_H_MAKE(TC_H_ROOT, 0))
autohandle = TC_H_MAKE(0x80000000U, 0);
- } while (qdisc_lookup(dev, autohandle) && --i > 0);
+ if (!qdisc_lookup(dev, autohandle))
+ return autohandle;
+ cond_resched();
+ } while (--i > 0);
- return i > 0 ? autohandle : 0;
+ return 0;
}
void qdisc_tree_decrease_qlen(struct Qdisc *sch, unsigned int n)
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