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incubator-nuttx
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SMP: Fix a gap where we may try to make modifications to the task lists without being in a critical sections. That permits concurrent access to the tasks lists and many subtle problems. This fix just remains in the critical section throughout the operation (and possible until the task is restore in the event of a context switch). Makes a big difference in stability

This commit is contained in:
Gregory Nutt 2016-12-28 13:58:24 -06:00
parent 88da65ad8a
commit 96394f339e
2 changed files with 21 additions and 13 deletions
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2
configs/sabre-6quad/smp/defconfig
View File

@ -315,7 +315,7 @@ CONFIG_USER_ENTRYPOINT="nsh_main"
CONFIG_RR_INTERVAL=200
# CONFIG_SCHED_SPORADIC is not set
CONFIG_TASK_NAME_SIZE=31
CONFIG_MAX_TASKS=16
CONFIG_MAX_TASKS=32
# CONFIG_SCHED_HAVE_PARENT is not set
CONFIG_SCHED_WAITPID=y

32
sched/irq/irq_csection.c
View File

@ -504,16 +504,14 @@ void leave_critical_section(irqstate_t flags)
DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
(g_cpu_irqset & (1 << cpu)) != 0);
rtcb->irqcount = 0;
spin_clrbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
&g_cpu_irqlock);
/* Check if releasing the lock held by this CPU will unlock the
* critical section.
*/
/* Have all CPUs released the lock? */
if (!spin_islocked(&g_cpu_irqlock))
if ((g_cpu_irqset & ~(1 << cpu)) == 0)
{
/* Check if there are pending tasks and that pre-emption
* is also enabled. This is necessary becaue we may have
/* Yes.. Check if there are pending tasks and that pre-emption
* is also enabled. This is necessary because we may have
* deferred the up_release_pending() call in sched_unlock()
* because we were within a critical section then.
*/
@ -522,15 +520,25 @@ void leave_critical_section(irqstate_t flags)
!spin_islocked(&g_cpu_schedlock))
{
/* Release any ready-to-run tasks that have collected
* in g_pendingtasks if the scheduler is not locked.
*
* NOTE: This operation has a very high likelihood of
* causing this task to be switched out!
* in g_pendingtasks. NOTE: This operation has a very
* high likelihood of causing this task to be switched
* out!
*/
up_release_pending();
}
}
/* Now, possibly on return from a context switch, clear our
* count on the lock. If all CPUs have released the lock,
* then unlock the global IRQ spinlock.
*/
rtcb->irqcount = 0;
spin_clrbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
&g_cpu_irqlock);
/* Have all CPUs released the lock? */
}
}
}