kernel/linux.git/include/linux/wait_bit.h, branch v6.19.11

sched/wait: Remove unused bit_wait_io_timeout

2024-10-07T07:28:41+00:00

bit_wait_io_timeout has been unused since 2016's commit 62906027091f ("mm: add PageWaiters indicating tasks are waiting for a page bit") Remove it. Signed-off-by: "Dr. David Alan Gilbert" Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Tim Chen Link: https://lore.kernel.org/r/20241001234016.231696-1-linux@treblig.org

sched: add wait_var_event_io()

2024-10-07T07:28:39+00:00

It is not currently possible to wait wait_var_event for an io_schedule() style wait. This patch adds wait_var_event_io() for that purpose. Signed-off-by: NeilBrown Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240925053405.3960701-7-neilb@suse.de

sched: Add wait/wake interface for variable updated under a lock.

2024-10-07T07:28:38+00:00

Sometimes we need to wait for a condition to be true which must be testing while holding a lock. Correspondingly the condition is made true while holding the lock and the wake up is sent under the lock. This patch provides wake and wait interfaces which can be used for this situation when the lock is a mutex or a spinlock, or any other lock for which there are foo_lock() and foo_unlock() functions. Signed-off-by: NeilBrown Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240925053405.3960701-6-neilb@suse.de

sched: Add test_and_clear_wake_up_bit() and atomic_dec_and_wake_up()

2024-10-07T07:28:38+00:00

There are common patterns in the kernel of using test_and_clear_bit() before wake_up_bit(), and atomic_dec_and_test() before wake_up_var(). These combinations don't need extra barriers but sometimes include them unnecessarily. To help avoid the unnecessary barriers and to help discourage the general use of wake_up_bit/var (which is a fragile interface) introduce two combined functions which implement these patterns. Also add store_release_wake_up() which supports the task of simply setting a non-atomic variable and sending a wakeup. This pattern requires barriers which are often omitted. Signed-off-by: NeilBrown Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240925053405.3960701-5-neilb@suse.de

sched: Document wait_var_event() family of functions and wake_up_var()

2024-10-07T07:28:38+00:00

wake_up_var(), wait_var_event() and related interfaces are not documented but have important ordering requirements. This patch adds documentation and makes these requirements explicit. The return values for those wait_var_event_* functions which return a value are documented. Note that these are, perhaps surprisingly, sometimes different from comparable wait_on_bit() functions. Signed-off-by: NeilBrown Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240925053405.3960701-4-neilb@suse.de

sched: Improve documentation for wake_up_bit/wait_on_bit family of functions

2024-10-07T07:28:37+00:00

This patch revises the documention for wake_up_bit(), clear_and_wake_up_bit(), and all the wait_on_bit() family of functions. The new documentation places less emphasis on the pool of waitqueues used (an implementation detail) and focuses instead on details of how the functions behave. The barriers included in the wait functions and clear_and_wake_up_bit() and those required for wake_up_bit() are spelled out more clearly. The error statuses returned are given explicitly. The fact that the wait_on_bit_lock() function sets the bit is made more obvious. Signed-off-by: NeilBrown Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240925053405.3960701-3-neilb@suse.de

sched: change wake_up_bit() and related function to expect unsigned long *

2024-10-07T07:28:37+00:00

wake_up_bit() currently allows a "void *". While this isn't strictly a problem as the address is never dereferenced, it is inconsistent with the corresponding wait_on_bit() which requires "unsigned long *" and does dereference the pointer. Any code that needs to wait for a change in something other than an unsigned long would be better served by wake_up_var()/wait_var_event(). This patch changes all related "void *" to "unsigned long *". Reported-by: Linus Torvalds Signed-off-by: NeilBrown Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240925053405.3960701-2-neilb@suse.de

wait_on_bit: add an acquire memory barrier

2022-08-26T16:30:25+00:00

There are several places in the kernel where wait_on_bit is not followed by a memory barrier (for example, in drivers/md/dm-bufio.c:new_read). On architectures with weak memory ordering, it may happen that memory accesses that follow wait_on_bit are reordered before wait_on_bit and they may return invalid data. Fix this class of bugs by introducing a new function "test_bit_acquire" that works like test_bit, but has acquire memory ordering semantics. Signed-off-by: Mikulas Patocka Acked-by: Will Deacon Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

Add wait_var_event_interruptible()

2019-05-15T16:35:54+00:00

Add wait_var_event_interruptible() to allow interruptible waits for events. Signed-off-by: David Howells Acked-by: Peter Zijlstra (Intel)

bdi: wake up concurrent wb_shutdown() callers.

2018-05-03T15:25:47+00:00

syzbot is reporting hung tasks at wait_on_bit(WB_shutting_down) in wb_shutdown() [1]. This seems to be because commit 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") forgot to call wake_up_bit(WB_shutting_down) after clear_bit(WB_shutting_down). Introduce a helper function clear_and_wake_up_bit() and use it, in order to avoid similar errors in future. [1] https://syzkaller.appspot.com/bug?id=b297474817af98d5796bc544e1bb806fc3da0e5e Signed-off-by: Tetsuo Handa Reported-by: syzbot Fixes: 5318ce7d46866e1d ("bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()") Cc: Tejun Heo Reviewed-by: Jan Kara Suggested-by: Linus Torvalds Signed-off-by: Jens Axboe