Module Name: src
Committed By: hannken
Date: Tue Apr 15 09:50:45 UTC 2014
Modified Files:
src/sys/kern: vfs_trans.c
Log Message:
Fix a deadlock where one thread exits, enters fstrans_lwp_dtor()
and wants fstrans_lock. This thread holds the proc_lock.
Another thread holds fstrans_lock and runs pserialize_perform().
As the first thread holds the proc_lock, timeouts are blocked and
the second thread blocks forever in kpause().
Change fstrans_lwp_dtor() to invalidate, but not free its info
structs. No need to take fstrans_lock.
Change fstrans_get_lwp_info() to reuse invalidated info before
trying to allocate a new one.
To generate a diff of this commit:
cvs rdiff -u -r1.29 -r1.30 src/sys/kern/vfs_trans.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/vfs_trans.c
diff -u src/sys/kern/vfs_trans.c:1.29 src/sys/kern/vfs_trans.c:1.30
--- src/sys/kern/vfs_trans.c:1.29 Sat Nov 23 13:35:36 2013
+++ src/sys/kern/vfs_trans.c Tue Apr 15 09:50:45 2014
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_trans.c,v 1.29 2013/11/23 13:35:36 christos Exp $ */
+/* $NetBSD: vfs_trans.c,v 1.30 2014/04/15 09:50:45 hannken Exp $ */
/*-
* Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.29 2013/11/23 13:35:36 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.30 2014/04/15 09:50:45 hannken Exp $");
/*
* File system transaction operations.
@@ -82,7 +82,6 @@ static kcondvar_t fstrans_count_cv; /* F
static pserialize_t fstrans_psz; /* Pserialize state. */
static LIST_HEAD(fstrans_lwp_head, fstrans_lwp_info) fstrans_fli_head;
/* List of all fstrans_lwp_info. */
-static pool_cache_t fstrans_cache; /* Pool of struct fstrans_lwp_info. */
static void fstrans_lwp_dtor(void *);
static void fstrans_mount_dtor(struct mount *);
@@ -110,8 +109,6 @@ fstrans_init(void)
cv_init(&fstrans_count_cv, "fstcnt");
fstrans_psz = pserialize_create();
LIST_INIT(&fstrans_fli_head);
- fstrans_cache = pool_cache_init(sizeof(struct fstrans_lwp_info), 0, 0,
- 0, "fstrans", NULL, IPL_NONE, NULL, NULL, NULL);
}
/*
@@ -122,17 +119,16 @@ fstrans_lwp_dtor(void *arg)
{
struct fstrans_lwp_info *fli, *fli_next;
- mutex_enter(&fstrans_lock);
for (fli = arg; fli; fli = fli_next) {
KASSERT(fli->fli_trans_cnt == 0);
KASSERT(fli->fli_cow_cnt == 0);
if (fli->fli_mount != NULL)
fstrans_mount_dtor(fli->fli_mount);
fli_next = fli->fli_succ;
- LIST_REMOVE(fli, fli_list);
- pool_cache_put(fstrans_cache, fli);
+ fli->fli_mount = NULL;
+ membar_sync();
+ fli->fli_self = NULL;
}
- mutex_exit(&fstrans_lock);
}
/*
@@ -237,7 +233,21 @@ fstrans_get_lwp_info(struct mount *mp, b
}
}
if (fli == NULL) {
- fli = pool_cache_get(fstrans_cache, PR_WAITOK);
+ mutex_enter(&fstrans_lock);
+ LIST_FOREACH(fli, &fstrans_fli_head, fli_list) {
+ if (fli->fli_self == NULL) {
+ KASSERT(fli->fli_trans_cnt == 0);
+ KASSERT(fli->fli_cow_cnt == 0);
+ fli->fli_self = curlwp;
+ fli->fli_succ = lwp_getspecific(lwp_data_key);
+ lwp_setspecific(lwp_data_key, fli);
+ break;
+ }
+ }
+ mutex_exit(&fstrans_lock);
+ }
+ if (fli == NULL) {
+ fli = kmem_alloc(sizeof(*fli), KM_SLEEP);
mutex_enter(&fstrans_lock);
memset(fli, 0, sizeof(*fli));
fli->fli_self = curlwp;
