[PATCH] score: PR2181: Add _Thread_Yield()
Sebastian Huber
sebastian.huber at embedded-brains.de
Thu Jun 12 14:19:14 UTC 2014
The _Scheduler_Yield() was called by the executing thread with thread
dispatching disabled and interrupts enabled. The rtems_task_suspend()
is explicitly allowed in ISRs:
http://rtems.org/onlinedocs/doc-current/share/rtems/html/c_user/Interrupt-Manager-Directives-Allowed-from-an-ISR.html#Interrupt-Manager-Directives-Allowed-from-an-ISR
Unlike the other scheduler operations the locking was performed inside
the operation. This lead to the following race condition. Suppose a
ISR suspends the executing thread right before the yield scheduler
operation. Now the executing thread is not longer in the set of ready
threads. The typical scheduler operations did not check the thread
state and will now extract the thread again and enqueue it. This
corrupted data structures.
Add _Thread_Yield() and do the scheduler yield operation with interrupts
disabled. This has a negligible effect on the interrupt latency.
---
cpukit/posix/src/nanosleep.c | 3 +-
cpukit/posix/src/sched_yield.c | 7 +--
cpukit/rtems/src/taskwakeafter.c | 3 +-
cpukit/score/Makefile.am | 1 +
.../score/include/rtems/score/schedulersmpimpl.h | 21 ++++++++++
cpukit/score/include/rtems/score/threadimpl.h | 2 +
cpukit/score/src/schedulerdefaulttick.c | 4 +-
cpukit/score/src/scheduleredfyield.c | 7 ---
cpukit/score/src/schedulerprioritysmp.c | 14 +++---
cpukit/score/src/schedulerpriorityyield.c | 23 ++++-------
cpukit/score/src/schedulersimplesmp.c | 14 +++---
cpukit/score/src/schedulersimpleyield.c | 15 +------
cpukit/score/src/threadyield.c | 41 ++++++++++++++++++++
13 files changed, 98 insertions(+), 57 deletions(-)
create mode 100644 cpukit/score/src/threadyield.c
diff --git a/cpukit/posix/src/nanosleep.c b/cpukit/posix/src/nanosleep.c
index ebaef33..54902b9 100644
--- a/cpukit/posix/src/nanosleep.c
+++ b/cpukit/posix/src/nanosleep.c
@@ -22,7 +22,6 @@
#include <errno.h>
#include <rtems/seterr.h>
-#include <rtems/score/schedulerimpl.h>
#include <rtems/score/threadimpl.h>
#include <rtems/score/timespec.h>
#include <rtems/score/watchdogimpl.h>
@@ -65,7 +64,7 @@ int nanosleep(
if ( !ticks ) {
_Thread_Disable_dispatch();
executing = _Thread_Executing;
- _Scheduler_Yield( _Scheduler_Get( executing ), executing );
+ _Thread_Yield( executing );
_Thread_Enable_dispatch();
if ( rmtp ) {
rmtp->tv_sec = 0;
diff --git a/cpukit/posix/src/sched_yield.c b/cpukit/posix/src/sched_yield.c
index 5293b19..e398fbf 100644
--- a/cpukit/posix/src/sched_yield.c
+++ b/cpukit/posix/src/sched_yield.c
@@ -21,16 +21,13 @@
#include <sched.h>
#include <rtems/score/percpu.h>
-#include <rtems/score/schedulerimpl.h>
#include <rtems/score/threaddispatch.h>
+#include <rtems/score/threadimpl.h>
int sched_yield( void )
{
- Thread_Control *executing;
-
_Thread_Disable_dispatch();
- executing = _Thread_Executing;
- _Scheduler_Yield( _Scheduler_Get( executing ), executing );
+ _Thread_Yield( _Thread_Executing );
_Thread_Enable_dispatch();
return 0;
}
diff --git a/cpukit/rtems/src/taskwakeafter.c b/cpukit/rtems/src/taskwakeafter.c
index 367b43a..88de6e5 100644
--- a/cpukit/rtems/src/taskwakeafter.c
+++ b/cpukit/rtems/src/taskwakeafter.c
@@ -20,7 +20,6 @@
#include <rtems/rtems/tasks.h>
#include <rtems/score/threadimpl.h>
-#include <rtems/score/schedulerimpl.h>
#include <rtems/score/watchdogimpl.h>
rtems_status_code rtems_task_wake_after(
@@ -37,7 +36,7 @@ rtems_status_code rtems_task_wake_after(
executing = _Thread_Executing;
if ( ticks == 0 ) {
- _Scheduler_Yield( _Scheduler_Get( executing ), executing );
+ _Thread_Yield( executing );
} else {
_Thread_Set_state( executing, STATES_DELAYING );
_Watchdog_Initialize(
diff --git a/cpukit/score/Makefile.am b/cpukit/score/Makefile.am
index 2fc31c5..6caefb5 100644
--- a/cpukit/score/Makefile.am
+++ b/cpukit/score/Makefile.am
@@ -287,6 +287,7 @@ libscore_a_SOURCES += src/thread.c src/threadchangepriority.c \
src/threadstackallocate.c src/threadstackfree.c src/threadstart.c \
src/threadstartmultitasking.c src/iterateoverthreads.c \
src/threadblockingoperationcancel.c
+libscore_a_SOURCES += src/threadyield.c
if HAS_SMP
libscore_a_SOURCES += src/smpbarrierwait.c
diff --git a/cpukit/score/include/rtems/score/schedulersmpimpl.h b/cpukit/score/include/rtems/score/schedulersmpimpl.h
index b4126b5..9d74434 100644
--- a/cpukit/score/include/rtems/score/schedulersmpimpl.h
+++ b/cpukit/score/include/rtems/score/schedulersmpimpl.h
@@ -672,6 +672,27 @@ static inline void _Scheduler_SMP_Change_priority(
}
}
+static inline void _Scheduler_SMP_Yield(
+ Scheduler_Context *context,
+ Thread_Control *thread,
+ Scheduler_SMP_Extract extract_from_ready,
+ Scheduler_SMP_Enqueue enqueue_fifo,
+ Scheduler_SMP_Enqueue enqueue_scheduled_fifo
+)
+{
+ Scheduler_SMP_Node *node = _Scheduler_SMP_Node_get( thread );
+
+ if ( node->state == SCHEDULER_SMP_NODE_SCHEDULED ) {
+ _Scheduler_SMP_Extract_from_scheduled( thread );
+
+ ( *enqueue_scheduled_fifo )( context, thread );
+ } else {
+ ( *extract_from_ready )( context, thread );
+
+ ( *enqueue_fifo )( context, thread );
+ }
+}
+
static inline void _Scheduler_SMP_Insert_scheduled_lifo(
Scheduler_Context *context,
Thread_Control *thread
diff --git a/cpukit/score/include/rtems/score/threadimpl.h b/cpukit/score/include/rtems/score/threadimpl.h
index 7e6681b..e90346c 100644
--- a/cpukit/score/include/rtems/score/threadimpl.h
+++ b/cpukit/score/include/rtems/score/threadimpl.h
@@ -186,6 +186,8 @@ bool _Thread_Restart(
Thread_Entry_numeric_type numeric_argument
);
+void _Thread_Yield( Thread_Control *executing );
+
bool _Thread_Set_life_protection( bool protect );
void _Thread_Life_action_handler(
diff --git a/cpukit/score/src/schedulerdefaulttick.c b/cpukit/score/src/schedulerdefaulttick.c
index 98cd05e..db67ca1 100644
--- a/cpukit/score/src/schedulerdefaulttick.c
+++ b/cpukit/score/src/schedulerdefaulttick.c
@@ -29,6 +29,8 @@ void _Scheduler_default_Tick(
Thread_Control *executing
)
{
+ (void) scheduler;
+
#ifdef __RTEMS_USE_TICKS_FOR_STATISTICS__
/*
* Increment the number of ticks this thread has been executing
@@ -69,7 +71,7 @@ void _Scheduler_default_Tick(
* currently executing thread is placed at the rear of the
* FIFO for this priority and a new heir is selected.
*/
- _Scheduler_Yield( scheduler, executing );
+ _Thread_Yield( executing );
executing->cpu_time_budget =
rtems_configuration_get_ticks_per_timeslice();
}
diff --git a/cpukit/score/src/scheduleredfyield.c b/cpukit/score/src/scheduleredfyield.c
index 9eb0782..d43448b 100644
--- a/cpukit/score/src/scheduleredfyield.c
+++ b/cpukit/score/src/scheduleredfyield.c
@@ -29,9 +29,6 @@ void _Scheduler_EDF_Yield(
Scheduler_EDF_Context *context =
_Scheduler_EDF_Get_context( scheduler );
Scheduler_EDF_Node *node = _Scheduler_EDF_Node_get( the_thread );
- ISR_Level level;
-
- _ISR_Disable( level );
/*
* The RBTree has more than one node, enqueue behind the tasks
@@ -40,9 +37,5 @@ void _Scheduler_EDF_Yield(
_RBTree_Extract( &context->Ready, &node->Node );
_RBTree_Insert( &context->Ready, &node->Node );
- _ISR_Flash( level );
-
_Scheduler_EDF_Schedule_body( scheduler, the_thread, false );
-
- _ISR_Enable( level );
}
diff --git a/cpukit/score/src/schedulerprioritysmp.c b/cpukit/score/src/schedulerprioritysmp.c
index 96b1689..bcbd26d 100644
--- a/cpukit/score/src/schedulerprioritysmp.c
+++ b/cpukit/score/src/schedulerprioritysmp.c
@@ -237,12 +237,12 @@ void _Scheduler_priority_SMP_Yield(
)
{
Scheduler_Context *context = _Scheduler_Get_context( scheduler );
- ISR_Level level;
- _ISR_Disable( level );
-
- _Scheduler_SMP_Extract_from_scheduled( thread );
- _Scheduler_priority_SMP_Enqueue_scheduled_fifo( context, thread );
-
- _ISR_Enable( level );
+ return _Scheduler_SMP_Yield(
+ context,
+ thread,
+ _Scheduler_priority_SMP_Extract_from_ready,
+ _Scheduler_priority_SMP_Enqueue_fifo,
+ _Scheduler_priority_SMP_Enqueue_scheduled_fifo
+ );
}
diff --git a/cpukit/score/src/schedulerpriorityyield.c b/cpukit/score/src/schedulerpriorityyield.c
index f2aeada..60bab39 100644
--- a/cpukit/score/src/schedulerpriorityyield.c
+++ b/cpukit/score/src/schedulerpriorityyield.c
@@ -19,7 +19,6 @@
#endif
#include <rtems/score/schedulerpriorityimpl.h>
-#include <rtems/score/isr.h>
#include <rtems/score/threadimpl.h>
void _Scheduler_priority_Yield(
@@ -29,23 +28,19 @@ void _Scheduler_priority_Yield(
{
Scheduler_priority_Node *node = _Scheduler_priority_Node_get( the_thread );
Chain_Control *ready_chain = node->Ready_queue.ready_chain;
- ISR_Level level;
(void) scheduler;
- _ISR_Disable( level );
- if ( !_Chain_Has_only_one_node( ready_chain ) ) {
- _Chain_Extract_unprotected( &the_thread->Object.Node );
- _Chain_Append_unprotected( ready_chain, &the_thread->Object.Node );
+ if ( !_Chain_Has_only_one_node( ready_chain ) ) {
+ _Chain_Extract_unprotected( &the_thread->Object.Node );
+ _Chain_Append_unprotected( ready_chain, &the_thread->Object.Node );
- _ISR_Flash( level );
-
- if ( _Thread_Is_heir( the_thread ) )
- _Thread_Heir = (Thread_Control *) _Chain_First( ready_chain );
- _Thread_Dispatch_necessary = true;
+ if ( _Thread_Is_heir( the_thread ) ) {
+ _Thread_Heir = (Thread_Control *) _Chain_First( ready_chain );
}
- else if ( !_Thread_Is_heir( the_thread ) )
- _Thread_Dispatch_necessary = true;
- _ISR_Enable( level );
+ _Thread_Dispatch_necessary = true;
+ } else if ( !_Thread_Is_heir( the_thread ) ) {
+ _Thread_Dispatch_necessary = true;
+ }
}
diff --git a/cpukit/score/src/schedulersimplesmp.c b/cpukit/score/src/schedulersimplesmp.c
index eb260ef..37458d6 100644
--- a/cpukit/score/src/schedulersimplesmp.c
+++ b/cpukit/score/src/schedulersimplesmp.c
@@ -302,12 +302,12 @@ void _Scheduler_simple_SMP_Yield(
)
{
Scheduler_Context *context = _Scheduler_Get_context( scheduler );
- ISR_Level level;
- _ISR_Disable( level );
-
- _Scheduler_SMP_Extract_from_scheduled( thread );
- _Scheduler_simple_SMP_Enqueue_scheduled_fifo( context, thread );
-
- _ISR_Enable( level );
+ return _Scheduler_SMP_Yield(
+ context,
+ thread,
+ _Scheduler_simple_SMP_Extract_from_ready,
+ _Scheduler_simple_SMP_Enqueue_fifo,
+ _Scheduler_simple_SMP_Enqueue_scheduled_fifo
+ );
}
diff --git a/cpukit/score/src/schedulersimpleyield.c b/cpukit/score/src/schedulersimpleyield.c
index 65578d0..b807530 100644
--- a/cpukit/score/src/schedulersimpleyield.c
+++ b/cpukit/score/src/schedulersimpleyield.c
@@ -19,7 +19,6 @@
#endif
#include <rtems/score/schedulersimpleimpl.h>
-#include <rtems/score/isr.h>
void _Scheduler_simple_Yield(
const Scheduler_Control *scheduler,
@@ -28,16 +27,8 @@ void _Scheduler_simple_Yield(
{
Scheduler_simple_Context *context =
_Scheduler_simple_Get_context( scheduler );
- ISR_Level level;
- _ISR_Disable( level );
-
- _Chain_Extract_unprotected( &the_thread->Object.Node );
- _Scheduler_simple_Insert_priority_fifo( &context->Ready, the_thread );
-
- _ISR_Flash( level );
-
- _Scheduler_simple_Schedule_body( scheduler, the_thread, false );
-
- _ISR_Enable( level );
+ _Chain_Extract_unprotected( &the_thread->Object.Node );
+ _Scheduler_simple_Insert_priority_fifo( &context->Ready, the_thread );
+ _Scheduler_simple_Schedule_body( scheduler, the_thread, false );
}
diff --git a/cpukit/score/src/threadyield.c b/cpukit/score/src/threadyield.c
new file mode 100644
index 0000000..b49e2b3
--- /dev/null
+++ b/cpukit/score/src/threadyield.c
@@ -0,0 +1,41 @@
+/**
+ * @file
+ *
+ * @brief Thread Yield
+ *
+ * @ingroup ScoreThread
+ */
+
+/*
+ * Copyright (c) 2014 embedded brains GmbH. All rights reserved.
+ *
+ * embedded brains GmbH
+ * Dornierstr. 4
+ * 82178 Puchheim
+ * Germany
+ * <rtems at embedded-brains.de>
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rtems.org/license/LICENSE.
+ */
+
+#if HAVE_CONFIG_H
+ #include "config.h"
+#endif
+
+#include <rtems/score/threadimpl.h>
+#include <rtems/score/schedulerimpl.h>
+
+void _Thread_Yield( Thread_Control *executing )
+{
+ ISR_Level level;
+
+ _ISR_Disable( level );
+
+ if ( _States_Is_ready( executing->current_state ) ) {
+ _Scheduler_Yield( _Scheduler_Get( executing ), executing );
+ }
+
+ _ISR_Enable( level );
+}
--
1.7.7
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