forked from mirrors/linux
2055da9738
So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.
Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.
To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:
struct wait_queue_head::task_list => ::head
struct wait_queue_entry::task_list => ::entry
For example, this code:
rqw->wait.task_list.next != &wait->task_list
... is was pretty unclear (to me) what it's doing, while now it's written this way:
rqw->wait.head.next != &wait->entry
... which makes it pretty clear that we are iterating a list until we see the head.
Other examples are:
list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
list_for_each_entry(wq, &fence->wait.task_list, task_list) {
... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:
list_for_each_entry_safe(pos, next, &x->head, entry) {
list_for_each_entry(wq, &fence->wait.head, entry) {
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
261 lines
9.1 KiB
C
261 lines
9.1 KiB
C
#ifndef _LINUX_WAIT_BIT_H
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#define _LINUX_WAIT_BIT_H
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/*
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* Linux wait-bit related types and methods:
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*/
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#include <linux/wait.h>
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struct wait_bit_key {
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void *flags;
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int bit_nr;
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#define WAIT_ATOMIC_T_BIT_NR -1
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unsigned long timeout;
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};
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struct wait_bit_queue_entry {
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struct wait_bit_key key;
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struct wait_queue_entry wq_entry;
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};
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#define __WAIT_BIT_KEY_INITIALIZER(word, bit) \
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{ .flags = word, .bit_nr = bit, }
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#define __WAIT_ATOMIC_T_KEY_INITIALIZER(p) \
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{ .flags = p, .bit_nr = WAIT_ATOMIC_T_BIT_NR, }
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typedef int wait_bit_action_f(struct wait_bit_key *key, int mode);
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void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit);
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int __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, wait_bit_action_f *action, unsigned int mode);
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int __wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, wait_bit_action_f *action, unsigned int mode);
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void wake_up_bit(void *word, int bit);
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void wake_up_atomic_t(atomic_t *p);
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int out_of_line_wait_on_bit(void *word, int, wait_bit_action_f *action, unsigned int mode);
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int out_of_line_wait_on_bit_timeout(void *word, int, wait_bit_action_f *action, unsigned int mode, unsigned long timeout);
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int out_of_line_wait_on_bit_lock(void *word, int, wait_bit_action_f *action, unsigned int mode);
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int out_of_line_wait_on_atomic_t(atomic_t *p, int (*)(atomic_t *), unsigned int mode);
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struct wait_queue_head *bit_waitqueue(void *word, int bit);
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extern void __init wait_bit_init(void);
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int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key);
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#define DEFINE_WAIT_BIT(name, word, bit) \
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struct wait_bit_queue_entry name = { \
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.key = __WAIT_BIT_KEY_INITIALIZER(word, bit), \
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.wq_entry = { \
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.private = current, \
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.func = wake_bit_function, \
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.entry = \
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LIST_HEAD_INIT((name).wq_entry.entry), \
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}, \
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}
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extern int bit_wait(struct wait_bit_key *key, int bit);
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extern int bit_wait_io(struct wait_bit_key *key, int bit);
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extern int bit_wait_timeout(struct wait_bit_key *key, int bit);
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extern int bit_wait_io_timeout(struct wait_bit_key *key, int bit);
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/**
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* wait_on_bit - wait for a bit to be cleared
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @mode: the task state to sleep in
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*
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* There is a standard hashed waitqueue table for generic use. This
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* is the part of the hashtable's accessor API that waits on a bit.
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* For instance, if one were to have waiters on a bitflag, one would
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* call wait_on_bit() in threads waiting for the bit to clear.
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* One uses wait_on_bit() where one is waiting for the bit to clear,
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* but has no intention of setting it.
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* Returned value will be zero if the bit was cleared, or non-zero
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* if the process received a signal and the mode permitted wakeup
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* on that signal.
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*/
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static inline int
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wait_on_bit(unsigned long *word, int bit, unsigned mode)
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{
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might_sleep();
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if (!test_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit(word, bit,
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bit_wait,
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mode);
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}
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/**
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* wait_on_bit_io - wait for a bit to be cleared
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @mode: the task state to sleep in
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*
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* Use the standard hashed waitqueue table to wait for a bit
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* to be cleared. This is similar to wait_on_bit(), but calls
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* io_schedule() instead of schedule() for the actual waiting.
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*
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* Returned value will be zero if the bit was cleared, or non-zero
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* if the process received a signal and the mode permitted wakeup
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* on that signal.
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*/
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static inline int
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wait_on_bit_io(unsigned long *word, int bit, unsigned mode)
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{
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might_sleep();
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if (!test_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit(word, bit,
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bit_wait_io,
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mode);
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}
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/**
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* wait_on_bit_timeout - wait for a bit to be cleared or a timeout elapses
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @mode: the task state to sleep in
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* @timeout: timeout, in jiffies
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*
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* Use the standard hashed waitqueue table to wait for a bit
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* to be cleared. This is similar to wait_on_bit(), except also takes a
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* timeout parameter.
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*
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* Returned value will be zero if the bit was cleared before the
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* @timeout elapsed, or non-zero if the @timeout elapsed or process
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* received a signal and the mode permitted wakeup on that signal.
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*/
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static inline int
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wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode,
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unsigned long timeout)
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{
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might_sleep();
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if (!test_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit_timeout(word, bit,
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bit_wait_timeout,
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mode, timeout);
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}
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/**
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* wait_on_bit_action - wait for a bit to be cleared
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @action: the function used to sleep, which may take special actions
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* @mode: the task state to sleep in
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*
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* Use the standard hashed waitqueue table to wait for a bit
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* to be cleared, and allow the waiting action to be specified.
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* This is like wait_on_bit() but allows fine control of how the waiting
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* is done.
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*
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* Returned value will be zero if the bit was cleared, or non-zero
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* if the process received a signal and the mode permitted wakeup
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* on that signal.
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*/
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static inline int
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wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action,
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unsigned mode)
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{
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might_sleep();
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if (!test_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit(word, bit, action, mode);
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}
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/**
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* wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @mode: the task state to sleep in
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*
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* There is a standard hashed waitqueue table for generic use. This
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* is the part of the hashtable's accessor API that waits on a bit
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* when one intends to set it, for instance, trying to lock bitflags.
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* For instance, if one were to have waiters trying to set bitflag
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* and waiting for it to clear before setting it, one would call
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* wait_on_bit() in threads waiting to be able to set the bit.
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* One uses wait_on_bit_lock() where one is waiting for the bit to
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* clear with the intention of setting it, and when done, clearing it.
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*
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* Returns zero if the bit was (eventually) found to be clear and was
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* set. Returns non-zero if a signal was delivered to the process and
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* the @mode allows that signal to wake the process.
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*/
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static inline int
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wait_on_bit_lock(unsigned long *word, int bit, unsigned mode)
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{
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might_sleep();
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if (!test_and_set_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit_lock(word, bit, bit_wait, mode);
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}
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/**
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* wait_on_bit_lock_io - wait for a bit to be cleared, when wanting to set it
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @mode: the task state to sleep in
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*
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* Use the standard hashed waitqueue table to wait for a bit
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* to be cleared and then to atomically set it. This is similar
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* to wait_on_bit(), but calls io_schedule() instead of schedule()
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* for the actual waiting.
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*
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* Returns zero if the bit was (eventually) found to be clear and was
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* set. Returns non-zero if a signal was delivered to the process and
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* the @mode allows that signal to wake the process.
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*/
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static inline int
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wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode)
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{
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might_sleep();
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if (!test_and_set_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit_lock(word, bit, bit_wait_io, mode);
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}
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/**
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* wait_on_bit_lock_action - wait for a bit to be cleared, when wanting to set it
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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* @action: the function used to sleep, which may take special actions
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* @mode: the task state to sleep in
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*
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* Use the standard hashed waitqueue table to wait for a bit
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* to be cleared and then to set it, and allow the waiting action
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* to be specified.
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* This is like wait_on_bit() but allows fine control of how the waiting
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* is done.
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*
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* Returns zero if the bit was (eventually) found to be clear and was
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* set. Returns non-zero if a signal was delivered to the process and
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* the @mode allows that signal to wake the process.
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*/
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static inline int
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wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action,
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unsigned mode)
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{
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might_sleep();
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if (!test_and_set_bit(bit, word))
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return 0;
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return out_of_line_wait_on_bit_lock(word, bit, action, mode);
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}
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/**
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* wait_on_atomic_t - Wait for an atomic_t to become 0
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* @val: The atomic value being waited on, a kernel virtual address
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* @action: the function used to sleep, which may take special actions
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* @mode: the task state to sleep in
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*
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* Wait for an atomic_t to become 0. We abuse the bit-wait waitqueue table for
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* the purpose of getting a waitqueue, but we set the key to a bit number
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* outside of the target 'word'.
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*/
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static inline
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int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
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{
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might_sleep();
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if (atomic_read(val) == 0)
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return 0;
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return out_of_line_wait_on_atomic_t(val, action, mode);
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}
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#endif /* _LINUX_WAIT_BIT_H */
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