The attached patch fixes long scheduling latencies caused by access to the
/proc/net/tcp file.  The seqfile functions keep softirqs disabled for a
very long time (i've seen reports of 20+ msecs, if there are enough sockets
in the system).  With the attached patch it's below 100 usecs.

The cond_resched_softirq() relies on the implicit knowledge that this code
executes in process context and runs with softirqs disabled.

Potentially enabling softirqs means that the socket list might change
between buckets - but this is not an issue since seqfiles have a 4K
iteration granularity anyway and /proc/net/tcp is often (much) larger than
that.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>