[MIPS] SMTC: Fix recursion in instant IPI replay code.
local_irq_restore -> raw_local_irq_restore -> irq_restore_epilog ->
smtc_ipi_replay -> smtc_ipi_dq -> spin_unlock_irqrestore ->
_spin_unlock_irqrestore -> local_irq_restore
The recursion does abort when there is no more IPI queued for a CPU, so
this isn't usually fatal which is why we got away with this for so long
until this was discovered by code inspection.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/smtc.c b/arch/mips/kernel/smtc.c
index e50fe20..5dcfab6 100644
--- a/arch/mips/kernel/smtc.c
+++ b/arch/mips/kernel/smtc.c
@@ -999,10 +999,17 @@
/*
* SMTC-specific hacks invoked from elsewhere in the kernel.
+ *
+ * smtc_ipi_replay is called from raw_local_irq_restore which is only ever
+ * called with interrupts disabled. We do rely on interrupts being disabled
+ * here because using spin_lock_irqsave()/spin_unlock_irqrestore() would
+ * result in a recursive call to raw_local_irq_restore().
*/
-void smtc_ipi_replay(void)
+static void __smtc_ipi_replay(void)
{
+ unsigned int cpu = smp_processor_id();
+
/*
* To the extent that we've ever turned interrupts off,
* we may have accumulated deferred IPIs. This is subtle.
@@ -1017,17 +1024,30 @@
* is clear, and we'll handle it as a real pseudo-interrupt
* and not a pseudo-pseudo interrupt.
*/
- if (IPIQ[smp_processor_id()].depth > 0) {
- struct smtc_ipi *pipi;
- extern void self_ipi(struct smtc_ipi *);
+ if (IPIQ[cpu].depth > 0) {
+ while (1) {
+ struct smtc_ipi_q *q = &IPIQ[cpu];
+ struct smtc_ipi *pipi;
+ extern void self_ipi(struct smtc_ipi *);
- while ((pipi = smtc_ipi_dq(&IPIQ[smp_processor_id()]))) {
+ spin_lock(&q->lock);
+ pipi = __smtc_ipi_dq(q);
+ spin_unlock(&q->lock);
+ if (!pipi)
+ break;
+
self_ipi(pipi);
- smtc_cpu_stats[smp_processor_id()].selfipis++;
+ smtc_cpu_stats[cpu].selfipis++;
}
}
}
+void smtc_ipi_replay(void)
+{
+ raw_local_irq_disable();
+ __smtc_ipi_replay();
+}
+
EXPORT_SYMBOL(smtc_ipi_replay);
void smtc_idle_loop_hook(void)
@@ -1132,7 +1152,13 @@
* is in use, there should never be any.
*/
#ifndef CONFIG_MIPS_MT_SMTC_INSTANT_REPLAY
- smtc_ipi_replay();
+ {
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __smtc_ipi_replay();
+ local_irq_restore(flags);
+ }
#endif /* CONFIG_MIPS_MT_SMTC_INSTANT_REPLAY */
}
