[PATCH] xmon fixes for 2.6

[John Rose]

This patch was written mostly by Jake Moilanen.  It fixes problems
that prevented the use of xmon breakpoints on pSeries LPAR systems.
Also updates help text to reflect obsolete subcommands, and adds
some necessary lines for single stepping.

If there are no comments on this, will push soon (thurs?).

Thanks-
John

diff -Nru a/arch/ppc64/xmon/xmon.c b/arch/ppc64/xmon/xmon.c
--- a/arch/ppc64/xmon/xmon.c	Tue Dec 16 17:49:24 2003
+++ b/arch/ppc64/xmon/xmon.c	Tue Dec 16 17:49:24 2003
@@ -37,9 +37,10 @@
 #define skipbl	xmon_skipbl

 #ifdef CONFIG_SMP
-unsigned long cpus_in_xmon = 0;
+volatile unsigned long cpus_in_xmon = 0;
 static unsigned long got_xmon = 0;
 static volatile int take_xmon = -1;
+static volatile int leaving_xmon = 0;
 #endif /* CONFIG_SMP */

 static unsigned long adrs;
@@ -162,7 +163,6 @@
   mz	zero a block of memory\n\
   mx	translation information for an effective address\n\
   mi	show information about memory allocation\n\
-  M	print System.map\n\
   p 	show the task list\n\
   r	print registers\n\
   s	single step\n\
@@ -227,7 +227,7 @@
 xmon(struct pt_regs *excp)
 {
 	struct pt_regs regs;
-	int cmd;
+	int cmd = 0;
 	unsigned long msr;

 	if (excp == NULL) {
@@ -285,9 +285,15 @@
 	xmon_regs[smp_processor_id()] = excp;
 	excprint(excp);
 #ifdef CONFIG_SMP
-	if (test_and_set_bit(smp_processor_id(), &cpus_in_xmon))
+	leaving_xmon = 0;
+	/* possible race condition here if a CPU is held up and gets
+	 * here while we are exiting */
+	if (test_and_set_bit(smp_processor_id(), &cpus_in_xmon)) {
+		/* xmon probably caused an exception itself */
+		printf("We are already in xmon\n");
 		for (;;)
 			;
+	}
 	while (test_and_set_bit(0, &got_xmon)) {
 		if (take_xmon == smp_processor_id()) {
 			take_xmon = -1;
@@ -304,6 +310,9 @@
 	if (cmd == 's') {
 		xmon_trace[smp_processor_id()] = SSTEP;
 		excp->msr |= MSR_SE;
+#ifdef CONFIG_SMP
+		take_xmon = smp_processor_id();
+#endif
 	} else if (at_breakpoint(excp->nip)) {
 		xmon_trace[smp_processor_id()] = BRSTEP;
 		excp->msr |= MSR_SE;
@@ -313,7 +322,9 @@
 	}
 	xmon_regs[smp_processor_id()] = 0;
 #ifdef CONFIG_SMP
-	clear_bit(0, &got_xmon);
+	leaving_xmon = 1;
+	if (cmd != 's')
+		clear_bit(0, &got_xmon);
 	clear_bit(smp_processor_id(), &cpus_in_xmon);
 #endif /* CONFIG_SMP */
 	set_msrd(msr);		/* restore interrupt enable */
@@ -421,8 +432,6 @@
 	int i;
 	struct bpt *bp;

-	if (systemcfg->platform != PLATFORM_PSERIES)
-		return;
 	bp = bpts;
 	for (i = 0; i < NBPTS; ++i, ++bp) {
 		if (!bp->enabled)
@@ -450,9 +459,6 @@
 	struct bpt *bp;
 	unsigned instr;

-	if (systemcfg->platform != PLATFORM_PSERIES)
-		return;
-
 	if ((cur_cpu_spec->cpu_features & CPU_FTR_DABR))
 		set_dabr(0);
 	if ((cur_cpu_spec->cpu_features & CPU_FTR_IABR))
@@ -478,11 +484,15 @@
 static int
 cmds(struct pt_regs *excp)
 {
-	int cmd;
+	int cmd = 0;

 	last_cmd = NULL;
 	for(;;) {
 #ifdef CONFIG_SMP
+		/* Need to check if we should take any commands on
+		   this CPU. */
+		if (leaving_xmon)
+			return cmd;
 		printf("%d:", smp_processor_id());
 #endif /* CONFIG_SMP */
 		printf("mon> ");
@@ -832,6 +842,12 @@
 				}
 			break;
 		}
+
+		if (!(systemcfg->platform & PLATFORM_PSERIES)) {
+			printf("Not supported for this platform\n");
+			break;
+		}
+
 		bp = at_breakpoint(a);
 		if (bp == 0) {
 			for (bp = bpts; bp < &bpts[NBPTS]; ++bp)


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