David Vrabel a13ca3d638 sunrpc: fix write space race causing stalls ... commit d48f9ce73c upstream. Write space becoming available may race with putting the task to sleep in xprt_wait_for_buffer_space(). The existing mechanism to avoid the race does not work. This (edited) partial trace illustrates the problem: [1] rpc_task_run_action: task:43546@5 ... action=call_transmit [2] xs_write_space <-xs_tcp_write_space [3] xprt_write_space <-xs_write_space [4] rpc_task_sleep: task:43546@5 ... [5] xs_write_space <-xs_tcp_write_space [1] Task 43546 runs but is out of write space. [2] Space becomes available, xs_write_space() clears the SOCKWQ_ASYNC_NOSPACE bit. [3] xprt_write_space() attemts to wake xprt->snd_task (== 43546), but this has not yet been queued and the wake up is lost. [4] xs_nospace() is called which calls xprt_wait_for_buffer_space() which queues task 43546. [5] The call to sk->sk_write_space() at the end of xs_nospace() (which is supposed to handle the above race) does not call xprt_write_space() as the SOCKWQ_ASYNC_NOSPACE bit is clear and thus the task is not woken. Fix the race by resetting the SOCKWQ_ASYNC_NOSPACE bit in xs_nospace() so the second call to sk->sk_write_space() calls xprt_write_space(). Suggested-by: Trond Myklebust <trondmy@primarydata.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2016-10-28 03:01:31 -04:00
..
auth_gss	SUNRPC: allow for upcalls for same uid but different gss service	2016-09-07 08:32:36 +02:00
xprtrdma	NFS client updates for Linux 4.4	2015-11-09 18:11:22 -08:00
addr.c
auth_generic.c
auth_null.c
auth_unix.c
auth.c
backchannel_rqst.c	SUNRPC: Fix callback channel	2015-12-07 13:04:59 -08:00
cache.c	sunrpc/cache: drop reference when sunrpc_cache_pipe_upcall() detects a race	2016-05-04 14:48:54 -07:00
clnt.c	nfsd4/rpc: move backchannel create logic into rpc code	2016-07-27 09:47:30 -07:00
debugfs.c
Kconfig
Makefile
netns.h
rpc_pipe.c
rpcb_clnt.c
sched.c	sched/wait: Fix the signal handling fix	2015-12-13 14:30:59 -08:00
socklib.c
stats.c
sunrpc_syms.c
sunrpc.h
svc_xprt.c
svc.c	NFS: Don't drop CB requests with invalid principals	2016-10-07 15:23:45 +02:00
svcauth_unix.c
svcauth.c
svcsock.c	svcrpc: document lack of some memory barriers	2015-11-10 17:02:47 -05:00
sysctl.c	Sunrpc: Supports hexadecimal number for sysctl files of sunrpc debug	2015-11-03 15:56:49 -05:00
timer.c
xdr.c
xprt.c
xprtsock.c	sunrpc: fix write space race causing stalls	2016-10-28 03:01:31 -04:00