Commit b8ee3e6d authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

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: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210601074801.617363-1-naveen.n.rao@linux.vnet.ibm.com
parent dcf57af2

arch/powerpc/xmon/xmon.c

+126 −22
Original line number Diff line number Diff line
@@ -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 xmon_switch_cpu(cpu);

}

	return 1;

#else

static int cpu_cmd(void)

{

	return 0;

#endif /* CONFIG_SMP */

}

#endif /* CONFIG_SMP */



static unsigned short fcstab[256] = {

	0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,