From bd0f9b356d00aa241ced36fb075a07041c28d3b8 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 7 Mar 2017 15:33:14 -0800
Subject: [PATCH] sched/headers: fix up header file dependency on
<linux/sched/signal.h>
The scheduler header file split and cleanups ended up exposing a few
nasty header file dependencies, and in particular it showed how we in
<linux/wait.h> ended up depending on "signal_pending()", which now comes
from <linux/sched/signal.h>.
That's a very subtle and annoying dependency, which already caused a
semantic merge conflict (see commit e58bc927835a "Pull overlayfs updates
from Miklos Szeredi", which added that fixup in the merge commit).
It turns out that we can avoid this dependency _and_ improve code
generation by moving the guts of the fairly nasty helper #define
__wait_event_interruptible_locked() to out-of-line code. The code that
includes the signal_pending() check is all in the slow-path where we
actually go to sleep waiting for the event anyway, so using a helper
function is the right thing to do.
Using a helper function is also what we already did for the non-locked
versions, see the "__wait_event*()" macros and the "prepare_to_wait*()"
set of helper functions.
We might want to try to unify all these macro games, we have a _lot_ of
subtly different wait-event loops. But this is the minimal patch to fix
the annoying header dependency.
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/wait.h | 31 ++++++++++---------------------
kernel/sched/wait.c | 39 +++++++++++++++++++++++++++++++++++++++
2 files changed, 49 insertions(+), 21 deletions(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h
index aacb1282d19a3..db076ca7f11da 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -620,30 +620,19 @@ do { \
__ret; \
})
+extern int do_wait_intr(wait_queue_head_t *, wait_queue_t *);
+extern int do_wait_intr_irq(wait_queue_head_t *, wait_queue_t *);
-#define __wait_event_interruptible_locked(wq, condition, exclusive, irq) \
+#define __wait_event_interruptible_locked(wq, condition, exclusive, fn) \
({ \
- int __ret = 0; \
+ int __ret; \
DEFINE_WAIT(__wait); \
if (exclusive) \
__wait.flags |= WQ_FLAG_EXCLUSIVE; \
do { \
- if (likely(list_empty(&__wait.task_list))) \
- __add_wait_queue_tail(&(wq), &__wait); \
- set_current_state(TASK_INTERRUPTIBLE); \
- if (signal_pending(current)) { \
- __ret = -ERESTARTSYS; \
+ __ret = fn(&(wq), &__wait); \
+ if (__ret) \
break; \
- } \
- if (irq) \
- spin_unlock_irq(&(wq).lock); \
- else \
- spin_unlock(&(wq).lock); \
- schedule(); \
- if (irq) \
- spin_lock_irq(&(wq).lock); \
- else \
- spin_lock(&(wq).lock); \
} while (!(condition)); \
__remove_wait_queue(&(wq), &__wait); \
__set_current_state(TASK_RUNNING); \
@@ -676,7 +665,7 @@ do { \
*/
#define wait_event_interruptible_locked(wq, condition) \
((condition) \
- ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 0))
+ ? 0 : __wait_event_interruptible_locked(wq, condition, 0, do_wait_intr))
/**
* wait_event_interruptible_locked_irq - sleep until a condition gets true
@@ -703,7 +692,7 @@ do { \
*/
#define wait_event_interruptible_locked_irq(wq, condition) \
((condition) \
- ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 1))
+ ? 0 : __wait_event_interruptible_locked(wq, condition, 0, do_wait_intr_irq))
/**
* wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true
@@ -734,7 +723,7 @@ do { \
*/
#define wait_event_interruptible_exclusive_locked(wq, condition) \
((condition) \
- ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 0))
+ ? 0 : __wait_event_interruptible_locked(wq, condition, 1, do_wait_intr))
/**
* wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true
@@ -765,7 +754,7 @@ do { \
*/
#define wait_event_interruptible_exclusive_locked_irq(wq, condition) \
((condition) \
- ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 1))
+ ? 0 : __wait_event_interruptible_locked(wq, condition, 1, do_wait_intr_irq))
#define __wait_event_killable(wq, condition) \
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 4d2ea6f255683..b8c84c6dee64b 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -242,6 +242,45 @@ long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
}
EXPORT_SYMBOL(prepare_to_wait_event);
+/*
+ * Note! These two wait functions are entered with the
+ * wait-queue lock held (and interrupts off in the _irq
+ * case), so there is no race with testing the wakeup
+ * condition in the caller before they add the wait
+ * entry to the wake queue.
+ */
+int do_wait_intr(wait_queue_head_t *wq, wait_queue_t *wait)
+{
+ if (likely(list_empty(&wait->task_list)))
+ __add_wait_queue_tail(wq, wait);
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+
+ spin_unlock(&wq->lock);
+ schedule();
+ spin_lock(&wq->lock);
+ return 0;
+}
+EXPORT_SYMBOL(do_wait_intr);
+
+int do_wait_intr_irq(wait_queue_head_t *wq, wait_queue_t *wait)
+{
+ if (likely(list_empty(&wait->task_list)))
+ __add_wait_queue_tail(wq, wait);
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+
+ spin_unlock_irq(&wq->lock);
+ schedule();
+ spin_lock_irq(&wq->lock);
+ return 0;
+}
+EXPORT_SYMBOL(do_wait_intr_irq);
+
/**
* finish_wait - clean up after waiting in a queue
* @q: waitqueue waited on
--
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