From b8ee3e6d6c5eec7e66de82449382f1a206db2046 Mon Sep 17 00:00:00 2001 From: "Naveen N. Rao" Date: Tue, 1 Jun 2021 13:18:01 +0530 Subject: [PATCH] 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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210601074801.617363-1-naveen.n.rao@linux.vnet.ibm.com --- arch/powerpc/xmon/xmon.c | 148 ++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 126 insertions(+), 22 deletions(-) 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; + + return xmon_switch_cpu(cpu); +} #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, -- 2.7.4