alistair23-linux/net/9p
Simon Derr 0462194d35 9P: Fix race in p9_read_work()
Race scenario between p9_read_work() and p9_poll_mux()

Data arrive, Rworksched is set, p9_read_work() is called.

thread A                                thread B

                                        p9_read_work()
                                                .
                                        reads data
                                                .
                                        checks if new data ready. No.
                                                .
                                        gets preempted
                                                .
More data arrive, p9_poll_mux() is called.      .
                                                .
                                                .
p9_poll_mux()                                   .
                                                .
if (!test_and_set_bit(Rworksched,               .
                      &m->wsched)) {            .
  schedule_work(&m->rq);                        .
}                                               .
                                                .
-> does not schedule work because               .
   Rworksched is set                            .
                                                .
                                        clear_bit(Rworksched, &m->wsched);
                                        return;

No work has been scheduled, and yet data are waiting.

Currently p9_read_work() checks if there is data to read,
and if not, it clears Rworksched.

I think it should clear Rworksched first, and then check if there is data to read.

Signed-off-by: Simon Derr <simon.derr@bull.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2012-09-17 14:54:11 -05:00
..
client.c net/9p: Check errno validity 2012-09-06 13:54:55 -05:00
error.c 9p: Reduce object size with CONFIG_NET_9P_DEBUG 2012-01-05 10:51:44 -06:00
Kconfig 9p: remove experimental tag from tested configurations 2011-05-25 08:46:38 -05:00
Makefile [net/9p] Preparation and helper functions for zero copy 2011-03-15 09:57:34 -05:00
mod.c 9p: Reduce object size with CONFIG_NET_9P_DEBUG 2012-01-05 10:51:44 -06:00
protocol.c 9p: fix min_t() casting in p9pdu_vwritef() 2012-06-27 15:26:24 -07:00
protocol.h net/9p: Convert net/9p protocol dumps to tracepoints 2011-10-24 11:13:12 -05:00
trans_common.c fs/9p: Update zero-copy implementation in 9p 2011-10-24 11:13:11 -05:00
trans_common.h fs/9p: Update zero-copy implementation in 9p 2011-10-24 11:13:11 -05:00
trans_fd.c 9P: Fix race in p9_read_work() 2012-09-17 14:54:11 -05:00
trans_rdma.c 9p: Reduce object size with CONFIG_NET_9P_DEBUG 2012-01-05 10:51:44 -06:00
trans_virtio.c net: Fix (nearly-)kernel-doc comments for various functions 2012-07-10 23:13:45 -07:00
util.c 9p: Reduce object size with CONFIG_NET_9P_DEBUG 2012-01-05 10:51:44 -06:00