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Add logic to handled nested calls to enter_critical_section() from interrupts handlers (with SMP).

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This commit is contained in:
Gregory Nutt 2016-11-16 22:45:08 -06:00
parent 0c3207e86e
commit 1c1564f0c1
1 changed files with 55 additions and 15 deletions
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70
sched/irq/irq_csection.c
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@ -66,6 +66,10 @@ volatile spinlock_t g_cpu_irqlock = SP_UNLOCKED;
volatile spinlock_t g_cpu_irqsetlock;
volatile cpu_set_t g_cpu_irqset;
/* Handles nested calls to enter_critical section from interrupt handlers */
volatile uint8_t g_cpu_nestcount[CONFIG_SMP_NCPUS];
#endif
/****************************************************************************
@ -115,6 +119,8 @@ irqstate_t enter_critical_section(void)
if (up_interrupt_context())
{
int cpu = this_cpu();
/* We are in an interrupt handler. How can this happen?
*
* 1. We were not in a critical section when the interrupt
@ -122,18 +128,34 @@ irqstate_t enter_critical_section(void)
* 2. We were in critical section, but up_irq_restore only
* disabled local interrupts on a different CPU;
* Interrupts could still be enabled on this CPU.
*
* Assert if these conditions are not true.
*/
DEBUGASSERT(!spin_islocked(&g_cpu_irqlock) ||
(g_cpu_irqset & (1 << this_cpu())) == 0);
/* Wait until we can get the spinlock (meaning that we are no
* longer in the critical section).
/* Handle nested calls to enter_critical_section() from the same
* interrupt.
*/
spin_lock(&g_cpu_irqlock);
if (g_cpu_nestcount[cpu] > 0)
{
DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
g_cpu_nestcount[cpu] < UINT8_MAX);
g_cpu_nestcount[cpu]++;
}
else
{
/* First call enter_critical_section. Test assumptions, then
* wait until we have the lock.
*/
DEBUGASSERT(!spin_islocked(&g_cpu_irqlock) ||
(g_cpu_irqset & (1 << this_cpu())) == 0);
/* Wait until we can get the spinlock (meaning that we are no
* longer in the critical section).
*/
spin_lock(&g_cpu_irqlock);
g_cpu_nestcount[cpu] = 1;
}
}
else
{
@ -246,17 +268,35 @@ void leave_critical_section(irqstate_t flags)
if (up_interrupt_context())
{
/* We are in an interrupt handler. Release the spinlock. */
int cpu = this_cpu();
DEBUGASSERT(spin_islocked(&g_cpu_irqlock));
/* We are in an interrupt handler. Check if the last call to
* enter_critical_section() was nested.
*/
spin_lock(&g_cpu_irqsetlock); /* Protects g_cpu_irqset */
if (g_cpu_irqset == 0)
if (g_cpu_nestcount[cpu] > 1)
{
spin_unlock(&g_cpu_irqlock);
}
/* Yes.. then just decrement the nesting count */
spin_unlock(&g_cpu_irqsetlock);
DEBUGASSERT(spin_islocked(&g_cpu_irqlock));
g_cpu_nestcount[cpu]--;
}
else
{
/* No, not nested. Release the spinlock. */
DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
g_cpu_nestcount[cpu] == 1);
spin_lock(&g_cpu_irqsetlock); /* Protects g_cpu_irqset */
if (g_cpu_irqset == 0)
{
spin_unlock(&g_cpu_irqlock);
}
spin_unlock(&g_cpu_irqsetlock);
g_cpu_nestcount[cpu] = 0;
}
}
else
{