MIPS: SMTC: Avoid queing multiple reschedule IPIs

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

MIPS: SMTC: Avoid queing multiple reschedule IPIs
Signed-off-by: Chris Dearman <chris@mips.com> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Jaidev Patwardhan · Ralf Baechle
1 parent 05cf20790b
Showing 2 changed files with 31 additions and 4 deletions Side-by-side Diff
arch/mips/include/asm/smtc_ipi.h
arch/mips/kernel/smtc.c
@@ -45,6 +45,7 @@
 	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)
@@ -75,7 +75,6 @@
  
 asiduse smtc_live_asid[MAX_SMTC_TLBS][MAX_SMTC_ASIDS];
  
-
 /*
  * Number of InterProcessor Interrupt (IPI) message buffers to allocate
  */
@@ -388,6 +387,7 @@
 		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 @@
 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 @@
 	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 @@
 	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 @@
 			 */
 			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 @@
 		 * 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 @@
 				 * 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);
 			}
...	...	@@ -45,6 +45,7 @@
45	45	spinlock_t lock;
46	46	struct smtc_ipi *tail;
47	47	int depth;
	48	+ int resched_flag; /* reschedule already queued */
48	49	};
49	50
50	51	static inline void smtc_ipi_nq(struct smtc_ipi_q q, struct smtc_ipi p)
...	...	@@ -75,7 +75,6 @@
75	75
76	76	asiduse smtc_live_asid[MAX_SMTC_TLBS][MAX_SMTC_ASIDS];
77	77
78		-
79	78	/*
80	79	* Number of InterProcessor Interrupt (IPI) message buffers to allocate
81	80	*/
...	...	@@ -388,6 +387,7 @@
388	387	IPIQ[i].head = IPIQ[i].tail = NULL;
389	388	spin_lock_init(&IPIQ[i].lock);
390	389	IPIQ[i].depth = 0;
	390	+ IPIQ[i].resched_flag = 0; /* No reschedules queued initially */
391	391	}
392	392
393	393	/* cpu_data index starts at zero */
394	394
395	395
...	...	@@ -741,11 +741,24 @@
741	741	static void smtc_ipi_qdump(void)
742	742	{
743	743	int i;
	744	+ struct smtc_ipi *temp;
744	745
745	746	for (i = 0; i < NR_CPUS ;i++) {
746		- printk("IPIQ[%d]: head = 0x%x, tail = 0x%x, depth = %d\n",
	747	+ pr_info("IPIQ[%d]: head = 0x%x, tail = 0x%x, depth = %d\n",
747	748	i, (unsigned)IPIQ[i].head, (unsigned)IPIQ[i].tail,
748	749	IPIQ[i].depth);
	750	+ temp = IPIQ[i].head;
	751	+
	752	+ while (temp != IPIQ[i].tail) {
	753	+ pr_debug("%d %d %d: ", temp->type, temp->dest,
	754	+ (int)temp->arg);
	755	+#ifdef SMTC_IPI_DEBUG
	756	+ pr_debug("%u %lu\n", temp->sender, temp->stamp);
	757	+#else
	758	+ pr_debug("\n");
	759	+#endif
	760	+ temp = temp->flink;
	761	+ }
749	762	}
750	763	}
751	764
752	765
...	...	@@ -784,11 +797,16 @@
784	797	int mtflags;
785	798	unsigned long tcrestart;
786	799	extern void r4k_wait_irqoff(void), __pastwait(void);
	800	+ int set_resched_flag = (type == LINUX_SMP_IPI &&
	801	+ action == SMP_RESCHEDULE_YOURSELF);
787	802
788	803	if (cpu == smp_processor_id()) {
789	804	printk("Cannot Send IPI to self!\n");
790	805	return;
791	806	}
	807	+ if (set_resched_flag && IPIQ[cpu].resched_flag != 0)
	808	+ return; /* There is a reschedule queued already */
	809	+
792	810	/* Set up a descriptor, to be delivered either promptly or queued */
793	811	pipi = smtc_ipi_dq(&freeIPIq);
794	812	if (pipi == NULL) {
...	...	@@ -801,6 +819,7 @@
801	819	pipi->dest = cpu;
802	820	if (cpu_data[cpu].vpe_id != cpu_data[smp_processor_id()].vpe_id) {
803	821	/* If not on same VPE, enqueue and send cross-VPE interrupt */
	822	+ IPIQ[cpu].resched_flag \|= set_resched_flag;
804	823	smtc_ipi_nq(&IPIQ[cpu], pipi);
805	824	LOCK_CORE_PRA();
806	825	settc(cpu_data[cpu].tc_id);
...	...	@@ -847,6 +866,7 @@
847	866	*/
848	867	write_tc_c0_tchalt(0);
849	868	UNLOCK_CORE_PRA();
	869	+ IPIQ[cpu].resched_flag \|= set_resched_flag;
850	870	smtc_ipi_nq(&IPIQ[cpu], pipi);
851	871	} else {
852	872	postdirect:
853	873
854	874
...	...	@@ -996,12 +1016,15 @@
996	1016	* already enabled.
997	1017	*/
998	1018	local_irq_save(flags);
999		-
1000	1019	spin_lock(&q->lock);
1001	1020	pipi = __smtc_ipi_dq(q);
1002	1021	spin_unlock(&q->lock);
1003		- if (pipi != NULL)
	1022	+ if (pipi != NULL) {
	1023	+ if (pipi->type == LINUX_SMP_IPI &&
	1024	+ (int)pipi->arg == SMP_RESCHEDULE_YOURSELF)
	1025	+ IPIQ[cpu].resched_flag = 0;
1004	1026	ipi_decode(pipi);
	1027	+ }
1005	1028	/*
1006	1029	* The use of the __raw_local restore isn't
1007	1030	* as obviously necessary here as in smtc_ipi_replay(),
...	...	@@ -1082,6 +1105,9 @@
1082	1105	* with interrupts off
1083	1106	*/
1084	1107	local_irq_save(flags);
	1108	+ if (pipi->type == LINUX_SMP_IPI &&
	1109	+ (int)pipi->arg == SMP_RESCHEDULE_YOURSELF)
	1110	+ IPIQ[cpu].resched_flag = 0;
1085	1111	ipi_decode(pipi);
1086	1112	local_irq_restore(flags);
1087	1113	}