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SUNRPC: Fix a potential race in xprt_connect() 

If an asynchronous connection attempt completes while another task is
in xprt_connect(), then the call to rpc_sleep_on() could end up
racing with the call to xprt_wake_pending_tasks().
So add a second test of the connection state after we've put the
task to sleep and set the XPRT_CONNECTING flag, when we know that there
can be no asynchronous connection attempts still in progress.

Fixes: 0b9e794313 ("SUNRPC: Move the test for XPRT_CONNECTING into...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust 2018-12-01 23:18:00 -05:00
parent 71700bb960
commit 0a9a4304f3
1 changed files with 9 additions and 2 deletions
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11
net/sunrpc/xprt.c
View File

@ -826,8 +826,15 @@ void xprt_connect(struct rpc_task *task)
return;
if (xprt_test_and_set_connecting(xprt))
return;
xprt->stat.connect_start = jiffies;
xprt->ops->connect(xprt, task);
/* Race breaker */
if (!xprt_connected(xprt)) {
xprt->stat.connect_start = jiffies;
xprt->ops->connect(xprt, task);
} else {
xprt_clear_connecting(xprt);
task->tk_status = 0;
rpc_wake_up_queued_task(&xprt->pending, task);
}
}
xprt_release_write(xprt, task);
}