powerpc/xmon: Add support for running a command on all cpus in xmon
It is sometimes desirable to run a command on all cpus in xmon. A
typical scenario is to obtain the backtrace from all cpus in xmon if
there is a soft lockup. Add rudimentary support for the same. The
command to be run on all cpus should be prefixed with 'c#'. As an
example, 'c#t' will run 't' command and produce a backtrace on all cpus
in xmon.
Since many xmon commands are not sensible for running in this manner, we
only allow a predefined list of commands -- 'r', 'S' and 't' for now.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210601074801.617363-1-naveen.n.rao@linux.vnet.ibm.com
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index dbc3848..12dcfb5 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -70,6 +70,9 @@ static cpumask_t cpus_in_xmon = CPU_MASK_NONE;
static unsigned long xmon_taken = 1;
static int xmon_owner;
static int xmon_gate;
+static int xmon_batch;
+static unsigned long xmon_batch_start_cpu;
+static cpumask_t xmon_batch_cpus = CPU_MASK_NONE;
#else
#define xmon_owner 0
#endif /* CONFIG_SMP */
@@ -133,6 +136,12 @@ static void prdump(unsigned long, long);
static int ppc_inst_dump(unsigned long, long, int);
static void dump_log_buf(void);
+#ifdef CONFIG_SMP
+static int xmon_switch_cpu(unsigned long);
+static int xmon_batch_next_cpu(void);
+static int batch_cmds(struct pt_regs *);
+#endif
+
#ifdef CONFIG_PPC_POWERNV
static void dump_opal_msglog(void);
#else
@@ -216,7 +225,8 @@ Commands:\n\
#ifdef CONFIG_SMP
"\
c print cpus stopped in xmon\n\
- c# try to switch to cpu number h (in hex)\n"
+ c# try to switch to cpu number h (in hex)\n\
+ c# $ run command '$' (one of 'r','S' or 't') on all cpus in xmon\n"
#endif
"\
C checksum\n\
@@ -644,7 +654,12 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
spin_cpu_relax();
touch_nmi_watchdog();
} else {
- if (!locked_down)
+ cmd = 1;
+#ifdef CONFIG_SMP
+ if (xmon_batch)
+ cmd = batch_cmds(regs);
+#endif
+ if (!locked_down && cmd)
cmd = cmds(regs);
if (locked_down || cmd != 0) {
/* exiting xmon */
@@ -1243,11 +1258,112 @@ static void bootcmds(void)
}
}
+#ifdef CONFIG_SMP
+static int xmon_switch_cpu(unsigned long cpu)
+{
+ int timeout;
+
+ xmon_taken = 0;
+ mb();
+ xmon_owner = cpu;
+ timeout = 10000000;
+ while (!xmon_taken) {
+ if (--timeout == 0) {
+ if (test_and_set_bit(0, &xmon_taken))
+ break;
+ /* take control back */
+ mb();
+ xmon_owner = smp_processor_id();
+ printf("cpu 0x%lx didn't take control\n", cpu);
+ return 0;
+ }
+ barrier();
+ }
+ return 1;
+}
+
+static int xmon_batch_next_cpu(void)
+{
+ unsigned long cpu;
+
+ while (!cpumask_empty(&xmon_batch_cpus)) {
+ cpu = cpumask_next_wrap(smp_processor_id(), &xmon_batch_cpus,
+ xmon_batch_start_cpu, true);
+ if (cpu == nr_cpumask_bits)
+ break;
+ if (xmon_batch_start_cpu == -1)
+ xmon_batch_start_cpu = cpu;
+ if (xmon_switch_cpu(cpu))
+ return 0;
+ cpumask_clear_cpu(cpu, &xmon_batch_cpus);
+ }
+
+ xmon_batch = 0;
+ printf("%x:mon> \n", smp_processor_id());
+ return 1;
+}
+
+static int batch_cmds(struct pt_regs *excp)
+{
+ int cmd;
+
+ /* simulate command entry */
+ cmd = xmon_batch;
+ termch = '\n';
+
+ last_cmd = NULL;
+ xmon_regs = excp;
+
+ printf("%x:", smp_processor_id());
+ printf("mon> ");
+ printf("%c\n", (char)cmd);
+
+ switch (cmd) {
+ case 'r':
+ prregs(excp); /* print regs */
+ break;
+ case 'S':
+ super_regs();
+ break;
+ case 't':
+ backtrace(excp);
+ break;
+ }
+
+ cpumask_clear_cpu(smp_processor_id(), &xmon_batch_cpus);
+
+ return xmon_batch_next_cpu();
+}
+
static int cpu_cmd(void)
{
-#ifdef CONFIG_SMP
unsigned long cpu, first_cpu, last_cpu;
- int timeout;
+
+ cpu = skipbl();
+ if (cpu == '#') {
+ xmon_batch = skipbl();
+ if (xmon_batch) {
+ switch (xmon_batch) {
+ case 'r':
+ case 'S':
+ case 't':
+ cpumask_copy(&xmon_batch_cpus, &cpus_in_xmon);
+ if (cpumask_weight(&xmon_batch_cpus) <= 1) {
+ printf("There are no other cpus in xmon\n");
+ break;
+ }
+ xmon_batch_start_cpu = -1;
+ if (!xmon_batch_next_cpu())
+ return 1;
+ break;
+ default:
+ printf("c# only supports 'r', 'S' and 't' commands\n");
+ }
+ xmon_batch = 0;
+ return 0;
+ }
+ }
+ termch = cpu;
if (!scanhex(&cpu)) {
/* print cpus waiting or in xmon */
@@ -1279,27 +1395,15 @@ static int cpu_cmd(void)
#endif
return 0;
}
- xmon_taken = 0;
- mb();
- xmon_owner = cpu;
- timeout = 10000000;
- while (!xmon_taken) {
- if (--timeout == 0) {
- if (test_and_set_bit(0, &xmon_taken))
- break;
- /* take control back */
- mb();
- xmon_owner = smp_processor_id();
- printf("cpu 0x%lx didn't take control\n", cpu);
- return 0;
- }
- barrier();
- }
- return 1;
-#else
- return 0;
-#endif /* CONFIG_SMP */
+
+ return xmon_switch_cpu(cpu);
}
+#else
+static int cpu_cmd(void)
+{
+ return 0;
+}
+#endif /* CONFIG_SMP */
static unsigned short fcstab[256] = {
0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,