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SMP: Enforce this rule: Tasks which are normally restored when sched_unlock() is called must remain pending (1) if we are in a critical section, i.e., g_cpu_irqlock is locked , or (2) other CPUs still have pre-emption disabled, i.e., g_cpu_schedlock is locked. In those cases, the release of the pending tasks must be deferred until those conditions are met.

This commit is contained in:
Gregory Nutt 2016-12-26 08:15:02 -06:00
parent d45a81d643
commit 849a5dc2a9
3 changed files with 29 additions and 12 deletions
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8
ChangeLog
View File

@ -13466,5 +13466,13 @@
(2016-12-24).
* STM32 F4: Allow dma in 1 bit mode in STM32F4xxx. From David Sidrane
(2016-12-24).
* termios.h: Fix CRTSCTS define to include input and output flow.
From Lorenz Meier (2016-12-26).
* SMP: Enforce this rule: Tasks which are normally restored when
sched_unlock() is called must remain pending (1) if we are in a
critical section, i.e., g_cpu_irqlock is locked , or (2) other CPUs
still have pre-emption disabled, i.e., g_cpu_schedlock is locked. In
those cases, the release of the pending tasks must be deferred until
those conditions are met (2016-12-26).
7.20 2017-xx-xx Gregory Nutt <gnutt@nuttx.org>

12
sched/irq/irq_csection.c
View File

@ -513,12 +513,9 @@ void leave_critical_section(irqstate_t flags)
if (!spin_islocked(&g_cpu_irqlock))
{
/* Check if there are pending tasks and that pre-emption
* is also enabled.
*
* REVISIT: Is there an issue here? up_release_pending()
* must be called from within a critical section but here
* we have just left the critical section. At least we
* still have interrupts disabled on this CPU.
* is also enabled. This is necessary becaue we may have
* deferred the up_release_pending() call in sched_unlock()
* because we were within a critical section then.
*/
if (g_pendingtasks.head != NULL &&
@ -529,9 +526,6 @@ void leave_critical_section(irqstate_t flags)
*
* NOTE: This operation has a very high likelihood of
* causing this task to be switched out!
*
* REVISIT: Should this not be done while we are in the
* critical section.
*/
up_release_pending();

21
sched/sched/sched_unlock.c
View File

@ -44,6 +44,7 @@
#include <nuttx/arch.h>
#include <nuttx/sched_note.h>
#include "irq/irq.h"
#include "sched/sched.h"
/****************************************************************************
@ -113,16 +114,30 @@ int sched_unlock(void)
#endif
/* Release any ready-to-run tasks that have collected in
* g_pendingtasks. In the SMP case, the scheduler remains
* locked if interrupts are disabled.
* g_pendingtasks.
*
* NOTE: This operation has a very high likelihood of causing
* this task to be switched out!
*/
#ifdef CONFIG_SMP
if (!spin_islocked(&g_cpu_schedlock) && g_pendingtasks.head != NULL)
/* In the SMP case, the tasks remains pend(1) if we are
* in a critical section, i.e., g_cpu_irqlock is locked , or (2)
* other CPUs still have pre-emption disabled, i.e.,
* g_cpu_schedlock is locked. In those cases, the release of the
* pending tasks must be deferred until those conditions are met.ing
*/
if (!spin_islocked(&g_cpu_schedlock) &&
!spin_islocked(&g_cpu_irqlock) &&
g_pendingtasks.head != NULL)
#else
/* In the single CPU case, decrementing irqcount to zero is
* sufficient to release the pending tasks. Further, in that
* configuration, critical sections and pre-emption can operate
* fully independently.
*/
if (g_pendingtasks.head != NULL)
#endif
{