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Avoid nfsiods acquiring/releasing a lock, then acquiring it again, before

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anyone else can get to it, by checking if a reply was received, and it
has thus become unnecessary to take the lock. From FreeBSD.

XXX I don't really like this, "locks" potentially suffer from the same
problem throughout the whole kernel; they should probably be FIFO everywhere.
This commit is contained in:
fvdl 1997-04-08 17:57:16 +00:00
parent 63d11b7577
commit b4e49cf0e9
1 changed files with 10 additions and 6 deletions
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16
sys/nfs/nfs_socket.c
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@ -1,4 +1,4 @@
/* $NetBSD: nfs_socket.c,v 1.35 1997/02/22 02:59:08 fvdl Exp $ */
/* $NetBSD: nfs_socket.c,v 1.36 1997/04/08 17:57:16 fvdl Exp $ */
/*
* Copyright (c) 1989, 1991, 1993, 1995
@ -637,13 +637,10 @@ nfs_reply(myrep)
* race conditions during a reconnect.
*/
error = nfs_rcvlock(myrep);
if (error == EALREADY)
return (0);
if (error)
return (error);
/* Already received, bye bye */
if (myrep->r_mrep != NULL) {
nfs_rcvunlock(&nmp->nm_flag);
return (0);
}
/*
* Get the next Rpc reply off the socket
*/
@ -1443,6 +1440,13 @@ nfs_rcvlock(rep)
*flagp |= NFSMNT_WANTRCV;
(void) tsleep((caddr_t)flagp, slpflag | (PZERO - 1), "nfsrcvlk",
slptimeo);
/* If our reply was received while we were sleeping,
* then just return without taking the lock to avoid a
* situation where a single iod could 'capture' the
* receive lock.
*/
if (rep->r_mrep != NULL)
return (EALREADY);
if (slpflag == PCATCH) {
slpflag = 0;
slptimeo = 2 * hz;