In a context where callbacks are called with spinlocks held, it is not
possible for drivers callbacks to wake up threads without holding any
spinlock. So, we need a mechanism to lock the scheduler when a spinlock
is grabbed. As xnpod_lock_sched/xnpod_unlock_sched may be a bit heavy
weight for this case, we try and make them a bit lighter, by avoiding
entering __xnpod_schedule when xnpod_unlock_sched is called without
the rescheduling bit set.
---
include/rtdm/rtdm_driver.h | 24 +++++++++++++++++++-----
ksrc/nucleus/pod.c | 7 ++++++-
ksrc/nucleus/sched-rt.c | 5 ++---
ksrc/nucleus/sched.c | 8 --------
4 files changed, 27 insertions(+), 17 deletions(-)
diff --git a/include/rtdm/rtdm_driver.h b/include/rtdm/rtdm_driver.h
index 3006d59..8b01f04 100644
--- a/include/rtdm/rtdm_driver.h
+++ b/include/rtdm/rtdm_driver.h
@@ -668,7 +668,9 @@ int rtdm_select_bind(int fd, rtdm_selector_t *selector,
spl_t __rtdm_s; \
\
xnlock_get_irqsave(&nklock, __rtdm_s); \
+ __xnpod_lock_sched(); \
code_block; \
+ __xnpod_unlock_sched(); \
xnlock_put_irqrestore(&nklock, __rtdm_s); \
}
#endif
@@ -730,6 +732,7 @@ typedef unsigned long rtdm_lockctx_t;
do { \
XENO_BUGON(RTDM, !rthal_local_irq_disabled()); \
rthal_spin_lock(lock); \
+ __xnpod_lock_sched(); \
} while (0)
#endif
@@ -749,7 +752,11 @@ typedef unsigned long rtdm_lockctx_t;
*
* Rescheduling: never.
*/
-#define rtdm_lock_put(lock) rthal_spin_unlock(lock)
+#define rtdm_lock_put(lock) \
+ do { \
+ rthal_spin_unlock(lock); \
+ __xnpod_unlock_sched(); \
+ } while (0)
/**
* Acquire lock and disable preemption
@@ -768,8 +775,11 @@ typedef unsigned long rtdm_lockctx_t;
*
* Rescheduling: never.
*/
-#define rtdm_lock_get_irqsave(lock, context) \
- rthal_spin_lock_irqsave(lock, context)
+#define rtdm_lock_get_irqsave(lock, context) \
+ do { \
+ rthal_spin_lock_irqsave(lock, context); \
+ __xnpod_lock_sched(); \
+ } while (0)
/**
* Release lock and restore preemption state
@@ -788,8 +798,12 @@ typedef unsigned long rtdm_lockctx_t;
*
* Rescheduling: possible.
*/
-#define rtdm_lock_put_irqrestore(lock, context) \
- rthal_spin_unlock_irqrestore(lock, context)
+#define rtdm_lock_put_irqrestore(lock, context) \
+ do { \
+ rthal_spin_unlock(lock); \
+ __xnpod_unlock_sched(); \
+ rthal_local_irq_restore(context); \
+ } while (0)
/**
* Disable preemption locally
diff --git a/ksrc/nucleus/pod.c b/ksrc/nucleus/pod.c
index 7c56abc..0f801fe 100644
--- a/ksrc/nucleus/pod.c
+++ b/ksrc/nucleus/pod.c
@@ -2203,6 +2203,12 @@ reschedule:
if (!need_resched)
goto signal_unlock_and_exit;
#endif /* !XENO_DEBUG(NUCLEUS) */
+ if (xnthread_test_state(curr, XNTHREAD_BLOCK_BITS|XNLOCK) == XNLOCK) {
+ /* scheduler is locked, thread is not suspending */
+ xnsched_set_self_resched(sched);
+ goto signal_unlock_and_exit;
+ }
+
zombie = xnthread_test_state(curr, XNZOMBIE);
next = xnsched_pick_next(sched);
@@ -2347,7 +2353,6 @@ void ___xnpod_unlock_sched(struct xnthread *curr)
{
if (--xnthread_lock_count(curr) == 0) {
xnthread_clear_state(curr, XNLOCK);
- xnsched_set_self_resched(curr->sched);
xnpod_schedule();
}
}
diff --git a/ksrc/nucleus/sched-rt.c b/ksrc/nucleus/sched-rt.c
index a167af6..8d17dca 100644
--- a/ksrc/nucleus/sched-rt.c
+++ b/ksrc/nucleus/sched-rt.c
@@ -81,11 +81,10 @@ static void xnsched_rt_rotate(struct xnsched *sched,
/*
* In case we picked the current thread, we have to make sure
* not to move it back to the runnable queue if it was blocked
- * before we were called. The same goes if the current thread
- * holds the scheduler lock.
+ * before we were called.
*/
if (thread == curr &&
- xnthread_test_state(curr, XNTHREAD_BLOCK_BITS | XNLOCK))
+ xnthread_test_state(curr, XNTHREAD_BLOCK_BITS))
return;
xnsched_putback(thread);
diff --git a/ksrc/nucleus/sched.c b/ksrc/nucleus/sched.c
index 3f4068b..9e8a656 100644
--- a/ksrc/nucleus/sched.c
+++ b/ksrc/nucleus/sched.c
@@ -208,14 +208,6 @@ struct xnthread *xnsched_pick_next(struct xnsched *sched)
if (!xnthread_test_state(curr, XNTHREAD_BLOCK_BITS | XNZOMBIE)) {
/*
- * Do not preempt the current thread if it holds the
- * scheduler lock.
- */
- if (xnthread_test_state(curr, XNLOCK)) {
- xnsched_set_self_resched(sched);
- return curr;
- }
- /*
* Push the current thread back to the runnable queue
* of the scheduling class it belongs to, if not yet
* linked to it (XNREADY tells us if it is).
--
1.7.2.5
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