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authorNeilBrown <neilb@suse.de>2014-07-07 09:16:04 +0400
committerIngo Molnar <mingo@kernel.org>2014-07-16 17:10:39 +0400
commit743162013d40ca612b4cb53d3a200dff2d9ab26e (patch)
treeb688e8afdbb96d18c7466b088b2dc21156a0bedd /include/linux/wait.h
parentd26fad5b38e1c4667d4f2604936e59c837caa54d (diff)
downloadlinux-743162013d40ca612b4cb53d3a200dff2d9ab26e.tar.xz
sched: Remove proliferation of wait_on_bit() action functions
The current "wait_on_bit" interface requires an 'action' function to be provided which does the actual waiting. There are over 20 such functions, many of them identical. Most cases can be satisfied by one of just two functions, one which uses io_schedule() and one which just uses schedule(). So: Rename wait_on_bit and wait_on_bit_lock to wait_on_bit_action and wait_on_bit_lock_action to make it explicit that they need an action function. Introduce new wait_on_bit{,_lock} and wait_on_bit{,_lock}_io which are *not* given an action function but implicitly use a standard one. The decision to error-out if a signal is pending is now made based on the 'mode' argument rather than being encoded in the action function. All instances of the old wait_on_bit and wait_on_bit_lock which can use the new version have been changed accordingly and their action functions have been discarded. wait_on_bit{_lock} does not return any specific error code in the event of a signal so the caller must check for non-zero and interpolate their own error code as appropriate. The wait_on_bit() call in __fscache_wait_on_invalidate() was ambiguous as it specified TASK_UNINTERRUPTIBLE but used fscache_wait_bit_interruptible as an action function. David Howells confirms this should be uniformly "uninterruptible" The main remaining user of wait_on_bit{,_lock}_action is NFS which needs to use a freezer-aware schedule() call. A comment in fs/gfs2/glock.c notes that having multiple 'action' functions is useful as they display differently in the 'wchan' field of 'ps'. (and /proc/$PID/wchan). As the new bit_wait{,_io} functions are tagged "__sched", they will not show up at all, but something higher in the stack. So the distinction will still be visible, only with different function names (gds2_glock_wait versus gfs2_glock_dq_wait in the gfs2/glock.c case). Since first version of this patch (against 3.15) two new action functions appeared, on in NFS and one in CIFS. CIFS also now uses an action function that makes the same freezer aware schedule call as NFS. Signed-off-by: NeilBrown <neilb@suse.de> Acked-by: David Howells <dhowells@redhat.com> (fscache, keys) Acked-by: Steven Whitehouse <swhiteho@redhat.com> (gfs2) Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steve French <sfrench@samba.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140707051603.28027.72349.stgit@notabene.brown Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/wait.h')
-rw-r--r--include/linux/wait.h115
1 files changed, 111 insertions, 4 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h
index bd68819f0815..73960ff09e56 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -854,11 +854,14 @@ int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
(wait)->flags = 0; \
} while (0)
+
+extern int bit_wait(void *);
+extern int bit_wait_io(void *);
+
/**
* wait_on_bit - wait for a bit to be cleared
* @word: the word being waited on, a kernel virtual address
* @bit: the bit of the word being waited on
- * @action: the function used to sleep, which may take special actions
* @mode: the task state to sleep in
*
* There is a standard hashed waitqueue table for generic use. This
@@ -867,9 +870,62 @@ int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
* call wait_on_bit() in threads waiting for the bit to clear.
* One uses wait_on_bit() where one is waiting for the bit to clear,
* but has no intention of setting it.
+ * Returned value will be zero if the bit was cleared, or non-zero
+ * if the process received a signal and the mode permitted wakeup
+ * on that signal.
+ */
+static inline int
+wait_on_bit(void *word, int bit, unsigned mode)
+{
+ if (!test_bit(bit, word))
+ return 0;
+ return out_of_line_wait_on_bit(word, bit,
+ bit_wait,
+ mode);
+}
+
+/**
+ * wait_on_bit_io - wait for a bit to be cleared
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ * @mode: the task state to sleep in
+ *
+ * Use the standard hashed waitqueue table to wait for a bit
+ * to be cleared. This is similar to wait_on_bit(), but calls
+ * io_schedule() instead of schedule() for the actual waiting.
+ *
+ * Returned value will be zero if the bit was cleared, or non-zero
+ * if the process received a signal and the mode permitted wakeup
+ * on that signal.
+ */
+static inline int
+wait_on_bit_io(void *word, int bit, unsigned mode)
+{
+ if (!test_bit(bit, word))
+ return 0;
+ return out_of_line_wait_on_bit(word, bit,
+ bit_wait_io,
+ mode);
+}
+
+/**
+ * wait_on_bit_action - wait for a bit to be cleared
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ * @action: the function used to sleep, which may take special actions
+ * @mode: the task state to sleep in
+ *
+ * Use the standard hashed waitqueue table to wait for a bit
+ * to be cleared, and allow the waiting action to be specified.
+ * This is like wait_on_bit() but allows fine control of how the waiting
+ * is done.
+ *
+ * Returned value will be zero if the bit was cleared, or non-zero
+ * if the process received a signal and the mode permitted wakeup
+ * on that signal.
*/
static inline int
-wait_on_bit(void *word, int bit, int (*action)(void *), unsigned mode)
+wait_on_bit_action(void *word, int bit, int (*action)(void *), unsigned mode)
{
if (!test_bit(bit, word))
return 0;
@@ -880,7 +936,6 @@ wait_on_bit(void *word, int bit, int (*action)(void *), unsigned mode)
* wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it
* @word: the word being waited on, a kernel virtual address
* @bit: the bit of the word being waited on
- * @action: the function used to sleep, which may take special actions
* @mode: the task state to sleep in
*
* There is a standard hashed waitqueue table for generic use. This
@@ -891,9 +946,61 @@ wait_on_bit(void *word, int bit, int (*action)(void *), unsigned mode)
* wait_on_bit() in threads waiting to be able to set the bit.
* One uses wait_on_bit_lock() where one is waiting for the bit to
* clear with the intention of setting it, and when done, clearing it.
+ *
+ * Returns zero if the bit was (eventually) found to be clear and was
+ * set. Returns non-zero if a signal was delivered to the process and
+ * the @mode allows that signal to wake the process.
+ */
+static inline int
+wait_on_bit_lock(void *word, int bit, unsigned mode)
+{
+ if (!test_and_set_bit(bit, word))
+ return 0;
+ return out_of_line_wait_on_bit_lock(word, bit, bit_wait, mode);
+}
+
+/**
+ * wait_on_bit_lock_io - wait for a bit to be cleared, when wanting to set it
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ * @mode: the task state to sleep in
+ *
+ * Use the standard hashed waitqueue table to wait for a bit
+ * to be cleared and then to atomically set it. This is similar
+ * to wait_on_bit(), but calls io_schedule() instead of schedule()
+ * for the actual waiting.
+ *
+ * Returns zero if the bit was (eventually) found to be clear and was
+ * set. Returns non-zero if a signal was delivered to the process and
+ * the @mode allows that signal to wake the process.
+ */
+static inline int
+wait_on_bit_lock_io(void *word, int bit, unsigned mode)
+{
+ if (!test_and_set_bit(bit, word))
+ return 0;
+ return out_of_line_wait_on_bit_lock(word, bit, bit_wait_io, mode);
+}
+
+/**
+ * wait_on_bit_lock_action - wait for a bit to be cleared, when wanting to set it
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ * @action: the function used to sleep, which may take special actions
+ * @mode: the task state to sleep in
+ *
+ * Use the standard hashed waitqueue table to wait for a bit
+ * to be cleared and then to set it, and allow the waiting action
+ * to be specified.
+ * This is like wait_on_bit() but allows fine control of how the waiting
+ * is done.
+ *
+ * Returns zero if the bit was (eventually) found to be clear and was
+ * set. Returns non-zero if a signal was delivered to the process and
+ * the @mode allows that signal to wake the process.
*/
static inline int
-wait_on_bit_lock(void *word, int bit, int (*action)(void *), unsigned mode)
+wait_on_bit_lock_action(void *word, int bit, int (*action)(void *), unsigned mode)
{
if (!test_and_set_bit(bit, word))
return 0;