diff options
| author | Simon Derr <simon.derr@bull.net> | 2012-09-17 15:16:31 +0200 |
|---|---|---|
| committer | Eric Van Hensbergen <ericvh@gmail.com> | 2012-10-11 12:03:31 -0500 |
| commit | 759f42987f98915764bad922ee123acb0eadbe33 (patch) | |
| tree | 57968c56307e7ea636a7558b15edb669dfb14399 | |
| parent | 584a8c13d58423462680907d4cc40d9929c9030a (diff) | |
9P: Fix race between p9_write_work() and p9_fd_request()
Race scenario:
thread A thread B
p9_write_work() p9_fd_request()
if (list_empty
(&m->unsent_req_list))
...
spin_lock(&client->lock);
req->status = REQ_STATUS_UNSENT;
list_add_tail(..., &m->unsent_req_list);
spin_unlock(&client->lock);
....
if (n & POLLOUT &&
!test_and_set_bit(Wworksched, &m->wsched)
schedule_work(&m->wq);
--> not done because Wworksched is set
clear_bit(Wworksched, &m->wsched);
return;
--> nobody will take care of sending the new request.
This is not very likely to happen though, because p9_write_work()
being called with an empty unsent_req_list is not frequent.
But this also means that taking the lock earlier will not be costly.
Signed-off-by: Simon Derr <simon.derr@bull.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
| -rw-r--r-- | net/9p/trans_fd.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index b2c308fffb8a..0031a8cf145d 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -453,12 +453,13 @@ static void p9_write_work(struct work_struct *work) } if (!m->wsize) { + spin_lock(&m->client->lock); if (list_empty(&m->unsent_req_list)) { clear_bit(Wworksched, &m->wsched); + spin_unlock(&m->client->lock); return; } - spin_lock(&m->client->lock); req = list_entry(m->unsent_req_list.next, struct p9_req_t, req_list); req->status = REQ_STATUS_SENT; |