[patch 3/4] Rework secondary SMT thread setup at boot

[nathanl at austin.ibm.com]

Our (ab)use of cpu_possible_map in setup_system to start secondary SMT
threads bothers me.  Mark such threads in cpu_possible_map during
early boot; let RTAS tell us which present cpus are still offline
later so we can start them.  Also change query_cpu_stopped to not BUG
when the RTAS query-cpu-stopped-state token is not available.

Signed-off-by: Nathan Lynch <nathanl at austin.ibm.com>


---


diff -puN arch/ppc64/kernel/prom.c~ppc64-fix-secondary-smt-thread-setup arch/ppc64/kernel/prom.c
--- 2.6-tip/arch/ppc64/kernel/prom.c~ppc64-fix-secondary-smt-thread-setup	2004-08-03 18:07:13.000000000 -0500
+++ 2.6-tip-nathanl/arch/ppc64/kernel/prom.c	2004-08-03 18:07:13.000000000 -0500
@@ -1076,6 +1076,8 @@ next:
 				cpu_set(cpuid, RELOC(cpu_available_map));
 				cpu_set(cpuid, RELOC(cpu_present_at_boot));
 				cpu_set(cpuid, RELOC(cpu_present_map));
+				cpu_set(cpuid, RELOC(cpu_possible_map));
+				_systemcfg->processorCount++;
 				prom_printf("available\n");
 			} else {
 				prom_printf("not available\n");
diff -puN arch/ppc64/kernel/setup.c~ppc64-fix-secondary-smt-thread-setup arch/ppc64/kernel/setup.c
--- 2.6-tip/arch/ppc64/kernel/setup.c~ppc64-fix-secondary-smt-thread-setup	2004-08-03 18:07:13.000000000 -0500
+++ 2.6-tip-nathanl/arch/ppc64/kernel/setup.c	2004-08-03 18:07:13.000000000 -0500
@@ -232,16 +232,17 @@ void setup_system(unsigned long r3, unsi
 		chrp_init(r3, r4, r5, r6, r7);

 #ifdef CONFIG_SMP
-		/* Start secondary threads on SMT systems */
-		for (i = 0; i < NR_CPUS; i++) {
-			if (cpu_available(i) && !cpu_possible(i)) {
+		/* Start secondary threads on SMT systems; primary threads
+		 * are already in the running state.
+		 */
+		for_each_present_cpu(i) {
+			if (query_cpu_stopped
+			    (get_hard_smp_processor_id(i)) == 0) {
 				printk("%16.16x : starting thread\n", i);
 				rtas_call(rtas_token("start-cpu"), 3, 1, &ret,
 					  get_hard_smp_processor_id(i),
 					  (u32)*((unsigned long *)pseries_secondary_smp_init),
 					  i);
-				cpu_set(i, cpu_possible_map);
-				systemcfg->processorCount++;
 			}
 		}
 #endif /* CONFIG_SMP */
diff -puN arch/ppc64/kernel/smp.c~ppc64-fix-secondary-smt-thread-setup arch/ppc64/kernel/smp.c
--- 2.6-tip/arch/ppc64/kernel/smp.c~ppc64-fix-secondary-smt-thread-setup	2004-08-03 18:07:13.000000000 -0500
+++ 2.6-tip-nathanl/arch/ppc64/kernel/smp.c	2004-08-03 18:07:13.000000000 -0500
@@ -225,7 +225,6 @@ static void __devinit smp_openpic_setup_
 	do_openpic_setup_cpu();
 }

-#ifdef CONFIG_HOTPLUG_CPU
 /* Get state of physical CPU.
  * Return codes:
  *	0	- The processor is in the RTAS stopped state
@@ -234,13 +233,14 @@ static void __devinit smp_openpic_setup_
  *	-1	- Hardware Error
  *	-2	- Hardware Busy, Try again later.
  */
-static int query_cpu_stopped(unsigned int pcpu)
+int query_cpu_stopped(unsigned int pcpu)
 {
 	int cpu_status;
 	int status, qcss_tok;

 	qcss_tok = rtas_token("query-cpu-stopped-state");
-	BUG_ON(qcss_tok == RTAS_UNKNOWN_SERVICE);
+	if (qcss_tok == RTAS_UNKNOWN_SERVICE)
+		return -1;
 	status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
 	if (status != 0) {
 		printk(KERN_ERR
@@ -251,6 +251,8 @@ static int query_cpu_stopped(unsigned in
 	return cpu_status;
 }

+#ifdef CONFIG_HOTPLUG_CPU
+
 int __cpu_disable(void)
 {
 	/* FIXME: go put this in a header somewhere */
diff -puN include/asm-ppc64/smp.h~ppc64-fix-secondary-smt-thread-setup include/asm-ppc64/smp.h
--- 2.6-tip/include/asm-ppc64/smp.h~ppc64-fix-secondary-smt-thread-setup	2004-08-03 18:07:13.000000000 -0500
+++ 2.6-tip-nathanl/include/asm-ppc64/smp.h	2004-08-03 18:07:13.000000000 -0500
@@ -73,6 +73,7 @@ void smp_init_pSeries(void);
 extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
 extern void cpu_die(void) __attribute__((noreturn));
+extern int query_cpu_stopped(unsigned int pcpu);
 #endif /* !(CONFIG_SMP) */

 #define get_hard_smp_processor_id(CPU) (paca[(CPU)].hw_cpu_id)

_

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