sched: Allow wait_on_bit_action() functions to support a timeout
It is currently not possible for various wait_on_bit functions
to implement a timeout.
While the "action" function that is called to do the waiting
could certainly use schedule_timeout(), there is no way to carry
forward the remaining timeout after a false wake-up.
As false-wakeups a clearly possible at least due to possible
hash collisions in bit_waitqueue(), this is a real problem.
The 'action' function is currently passed a pointer to the word
containing the bit being waited on. No current action functions
use this pointer. So changing it to something else will be a
little noisy but will have no immediate effect.
This patch changes the 'action' function to take a pointer to
the "struct wait_bit_key", which contains a pointer to the word
containing the bit so nothing is really lost.
It also adds a 'private' field to "struct wait_bit_key", which
is initialized to zero.
An action function can now implement a timeout with something
like
static int timed_out_waiter(struct wait_bit_key *key)
{
unsigned long waited;
if (key->private == 0) {
key->private = jiffies;
if (key->private == 0)
key->private -= 1;
}
waited = jiffies - key->private;
if (waited > 10 * HZ)
return -EAGAIN;
schedule_timeout(waited - 10 * HZ);
return 0;
}
If any other need for context in a waiter were found it would be
easy to use ->private for some other purpose, or even extend
"struct wait_bit_key".
My particular need is to support timeouts in nfs_release_page()
to avoid deadlocks with loopback mounted NFS.
While wait_on_bit_timeout() would be a cleaner interface, it
will not meet my need. I need the timeout to be sensitive to
the state of the connection with the server, which could change.
So I need to use an 'action' interface.
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steve French <sfrench@samba.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140707051604.28027.41257.stgit@notabene.brown
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 213c458..41de393 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1780,7 +1780,7 @@
* @word: long word containing the bit lock
*/
static int
-cifs_wait_bit_killable(void *word)
+cifs_wait_bit_killable(struct wait_bit_key *key)
{
if (fatal_signal_pending(current))
return -ERESTARTSYS;
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index b7b710e..abd37a3 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -75,7 +75,7 @@
* nfs_wait_bit_killable - helper for functions that are sleeping on bit locks
* @word: long word containing the bit lock
*/
-int nfs_wait_bit_killable(void *word)
+int nfs_wait_bit_killable(struct wait_bit_key *key)
{
if (fatal_signal_pending(current))
return -ERESTARTSYS;
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 82ddbf4..e0193d6 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -347,7 +347,7 @@
extern void nfs_clear_inode(struct inode *);
extern void nfs_evict_inode(struct inode *);
void nfs_zap_acl_cache(struct inode *inode);
-extern int nfs_wait_bit_killable(void *word);
+extern int nfs_wait_bit_killable(struct wait_bit_key *key);
/* super.c */
extern const struct super_operations nfs_sops;
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 6104d35..745a612d 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -117,7 +117,7 @@
set_bit(NFS_IO_INPROGRESS, &c->flags);
if (atomic_read(&c->io_count) == 0)
break;
- ret = nfs_wait_bit_killable(&c->flags);
+ ret = nfs_wait_bit_killable(&q.key);
} while (atomic_read(&c->io_count) != 0);
finish_wait(wq, &q.wait);
return ret;
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index ad7dbe2..1a89599 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -236,7 +236,7 @@
void rpc_free(void *);
int rpciod_up(void);
void rpciod_down(void);
-int __rpc_wait_for_completion_task(struct rpc_task *task, int (*)(void *));
+int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *);
#ifdef RPC_DEBUG
struct net;
void rpc_show_tasks(struct net *);
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 73960ff..6fb1ba5 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -25,6 +25,7 @@
void *flags;
int bit_nr;
#define WAIT_ATOMIC_T_BIT_NR -1
+ unsigned long private;
};
struct wait_bit_queue {
@@ -141,18 +142,19 @@
list_del(&old->task_list);
}
+typedef int wait_bit_action_f(struct wait_bit_key *);
void __wake_up(wait_queue_head_t *q, unsigned int mode, int nr, void *key);
void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key);
void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode, int nr, void *key);
void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr);
void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr);
void __wake_up_bit(wait_queue_head_t *, void *, int);
-int __wait_on_bit(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
-int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
+int __wait_on_bit(wait_queue_head_t *, struct wait_bit_queue *, wait_bit_action_f *, unsigned);
+int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, wait_bit_action_f *, unsigned);
void wake_up_bit(void *, int);
void wake_up_atomic_t(atomic_t *);
-int out_of_line_wait_on_bit(void *, int, int (*)(void *), unsigned);
-int out_of_line_wait_on_bit_lock(void *, int, int (*)(void *), unsigned);
+int out_of_line_wait_on_bit(void *, int, wait_bit_action_f *, unsigned);
+int out_of_line_wait_on_bit_lock(void *, int, wait_bit_action_f *, unsigned);
int out_of_line_wait_on_atomic_t(atomic_t *, int (*)(atomic_t *), unsigned);
wait_queue_head_t *bit_waitqueue(void *, int);
@@ -855,8 +857,8 @@
} while (0)
-extern int bit_wait(void *);
-extern int bit_wait_io(void *);
+extern int bit_wait(struct wait_bit_key *);
+extern int bit_wait_io(struct wait_bit_key *);
/**
* wait_on_bit - wait for a bit to be cleared
@@ -925,7 +927,7 @@
* on that signal.
*/
static inline int
-wait_on_bit_action(void *word, int bit, int (*action)(void *), unsigned mode)
+wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode)
{
if (!test_bit(bit, word))
return 0;
@@ -1000,7 +1002,7 @@
* the @mode allows that signal to wake the process.
*/
static inline int
-wait_on_bit_lock_action(void *word, int bit, int (*action)(void *), unsigned mode)
+wait_on_bit_lock_action(void *word, int bit, wait_bit_action_f *action, unsigned mode)
{
if (!test_and_set_bit(bit, word))
return 0;
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index a104879..15cab1a 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -319,14 +319,14 @@
*/
int __sched
__wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
- int (*action)(void *), unsigned mode)
+ wait_bit_action_f *action, unsigned mode)
{
int ret = 0;
do {
prepare_to_wait(wq, &q->wait, mode);
if (test_bit(q->key.bit_nr, q->key.flags))
- ret = (*action)(q->key.flags);
+ ret = (*action)(&q->key);
} while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
finish_wait(wq, &q->wait);
return ret;
@@ -334,7 +334,7 @@
EXPORT_SYMBOL(__wait_on_bit);
int __sched out_of_line_wait_on_bit(void *word, int bit,
- int (*action)(void *), unsigned mode)
+ wait_bit_action_f *action, unsigned mode)
{
wait_queue_head_t *wq = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wait, word, bit);
@@ -345,7 +345,7 @@
int __sched
__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
- int (*action)(void *), unsigned mode)
+ wait_bit_action_f *action, unsigned mode)
{
do {
int ret;
@@ -353,7 +353,7 @@
prepare_to_wait_exclusive(wq, &q->wait, mode);
if (!test_bit(q->key.bit_nr, q->key.flags))
continue;
- ret = action(q->key.flags);
+ ret = action(&q->key);
if (!ret)
continue;
abort_exclusive_wait(wq, &q->wait, mode, &q->key);
@@ -365,7 +365,7 @@
EXPORT_SYMBOL(__wait_on_bit_lock);
int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
- int (*action)(void *), unsigned mode)
+ wait_bit_action_f *action, unsigned mode)
{
wait_queue_head_t *wq = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wait, word, bit);
@@ -503,7 +503,7 @@
}
EXPORT_SYMBOL(wake_up_atomic_t);
-__sched int bit_wait(void *word)
+__sched int bit_wait(struct wait_bit_key *word)
{
if (signal_pending_state(current->state, current))
return 1;
@@ -512,7 +512,7 @@
}
EXPORT_SYMBOL(bit_wait);
-__sched int bit_wait_io(void *word)
+__sched int bit_wait_io(struct wait_bit_key *word)
{
if (signal_pending_state(current->state, current))
return 1;
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index c0365c1..9358c79 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -250,7 +250,7 @@
}
EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);
-static int rpc_wait_bit_killable(void *word)
+static int rpc_wait_bit_killable(struct wait_bit_key *key)
{
if (fatal_signal_pending(current))
return -ERESTARTSYS;
@@ -309,7 +309,7 @@
* to enforce taking of the wq->lock and hence avoid races with
* rpc_complete_task().
*/
-int __rpc_wait_for_completion_task(struct rpc_task *task, int (*action)(void *))
+int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *action)
{
if (action == NULL)
action = rpc_wait_bit_killable;