MIPS: SMTC: Avoid queing multiple reschedule IPIs

Signed-off-by: Chris Dearman <chris@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 31 insertions, 4 deletions

diff --git a/arch/mips/include/asm/smtc_ipi.h b/arch/mips/include/asm/smtc_ipi.h
index 8ce517574340..15278dbd7e79 100644
--- a/arch/mips/include/asm/smtc_ipi.h
+++ b/arch/mips/include/asm/smtc_ipi.h
@@ -45,6 +45,7 @@ struct smtc_ipi_q {
         spinlock_t lock;
         struct smtc_ipi *tail;
         int depth;
+        int resched_flag;       /* reschedule already queued */
 };
 
 static inline void smtc_ipi_nq(struct smtc_ipi_q *q, struct smtc_ipi *p)
diff --git a/arch/mips/kernel/smtc.c b/arch/mips/kernel/smtc.c
index 4d181df44a40..24630fd8ef60 100644
--- a/arch/mips/kernel/smtc.c
+++ b/arch/mips/kernel/smtc.c
@@ -75,7 +75,6 @@ unsigned long irq_hwmask[NR_IRQS];
 
 asiduse smtc_live_asid[MAX_SMTC_TLBS][MAX_SMTC_ASIDS];
 
-
 /*
  * Number of InterProcessor Interrupt (IPI) message buffers to allocate
  */
@@ -388,6 +387,7 @@ void smtc_prepare_cpus(int cpus)
                 IPIQ[i].head = IPIQ[i].tail = NULL;
                 spin_lock_init(&IPIQ[i].lock);
                 IPIQ[i].depth = 0;
+                IPIQ[i].resched_flag = 0; /* No reschedules queued initially */
         }
 
         /* cpu_data index starts at zero */
@@ -741,11 +741,24 @@ void smtc_forward_irq(unsigned int irq)
 static void smtc_ipi_qdump(void)
 {
         int i;
+        struct smtc_ipi *temp;
 
         for (i = 0; i < NR_CPUS ;i++) {
-                printk("IPIQ[%d]: head = 0x%x, tail = 0x%x, depth = %d\n",
+                pr_info("IPIQ[%d]: head = 0x%x, tail = 0x%x, depth = %d\n",
                         i, (unsigned)IPIQ[i].head, (unsigned)IPIQ[i].tail,
                         IPIQ[i].depth);
+                temp = IPIQ[i].head;
+
+                while (temp != IPIQ[i].tail) {
+                        pr_debug("%d %d %d: ", temp->type, temp->dest,
+                               (int)temp->arg);
+#ifdef  SMTC_IPI_DEBUG
+                    pr_debug("%u %lu\n", temp->sender, temp->stamp);
+#else
+                    pr_debug("\n");
+#endif
+                    temp = temp->flink;
+                }
         }
 }
 
@@ -784,11 +797,16 @@ void smtc_send_ipi(int cpu, int type, unsigned int action)
         int mtflags;
         unsigned long tcrestart;
         extern void r4k_wait_irqoff(void), __pastwait(void);
+        int set_resched_flag = (type == LINUX_SMP_IPI &&
+                                action == SMP_RESCHEDULE_YOURSELF);
 
         if (cpu == smp_processor_id()) {
                 printk("Cannot Send IPI to self!\n");
                 return;
         }
+        if (set_resched_flag && IPIQ[cpu].resched_flag != 0)
+                return; /* There is a reschedule queued already */
+
         /* Set up a descriptor, to be delivered either promptly or queued */
         pipi = smtc_ipi_dq(&freeIPIq);
         if (pipi == NULL) {
@@ -801,6 +819,7 @@ void smtc_send_ipi(int cpu, int type, unsigned int action)
         pipi->dest = cpu;
         if (cpu_data[cpu].vpe_id != cpu_data[smp_processor_id()].vpe_id) {
                 /* If not on same VPE, enqueue and send cross-VPE interrupt */
+                IPIQ[cpu].resched_flag |= set_resched_flag;
                 smtc_ipi_nq(&IPIQ[cpu], pipi);
                 LOCK_CORE_PRA();
                 settc(cpu_data[cpu].tc_id);
@@ -847,6 +866,7 @@ void smtc_send_ipi(int cpu, int type, unsigned int action)
                          */
                         write_tc_c0_tchalt(0);
                         UNLOCK_CORE_PRA();
+                        IPIQ[cpu].resched_flag |= set_resched_flag;
                         smtc_ipi_nq(&IPIQ[cpu], pipi);
                 } else {
 postdirect:
@@ -996,12 +1016,15 @@ void deferred_smtc_ipi(void)
                  * already enabled.
                  */
                 local_irq_save(flags);
-
                 spin_lock(&q->lock);
                 pipi = __smtc_ipi_dq(q);
                 spin_unlock(&q->lock);
-                if (pipi != NULL)
+                if (pipi != NULL) {
+                        if (pipi->type == LINUX_SMP_IPI &&
+                            (int)pipi->arg == SMP_RESCHEDULE_YOURSELF)
+                                IPIQ[cpu].resched_flag = 0;
                         ipi_decode(pipi);
+                }
                 /*
                  * The use of the __raw_local restore isn't
                  * as obviously necessary here as in smtc_ipi_replay(),
@@ -1082,6 +1105,9 @@ static irqreturn_t ipi_interrupt(int irq, void *dev_idm)
                                  * with interrupts off
                                  */
                                 local_irq_save(flags);
+                                if (pipi->type == LINUX_SMP_IPI &&
+                                    (int)pipi->arg == SMP_RESCHEDULE_YOURSELF)
+                                        IPIQ[cpu].resched_flag = 0;
                                 ipi_decode(pipi);
                                 local_irq_restore(flags);
                         }