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
This commit is contained in:
Naveen N. Rao
Michael Ellerman
parent
dcf57af201
commit
b8ee3e6d6c
@ -70,6 +70,9 @@ static cpumask_t cpus_in_xmon = CPU_MASK_NONE;
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static unsigned long xmon_taken = 1;
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static int xmon_owner;
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static int xmon_gate;
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static int xmon_batch;
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static unsigned long xmon_batch_start_cpu;
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static cpumask_t xmon_batch_cpus = CPU_MASK_NONE;
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#else
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#define xmon_owner 0
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#endif /* CONFIG_SMP */
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@ -133,6 +136,12 @@ static void prdump(unsigned long, long);
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static int ppc_inst_dump(unsigned long, long, int);
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static void dump_log_buf(void);
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#ifdef CONFIG_SMP
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static int xmon_switch_cpu(unsigned long);
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static int xmon_batch_next_cpu(void);
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static int batch_cmds(struct pt_regs *);
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#endif
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#ifdef CONFIG_PPC_POWERNV
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static void dump_opal_msglog(void);
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#else
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@ -216,7 +225,8 @@ Commands:\n\
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#ifdef CONFIG_SMP
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"\
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c print cpus stopped in xmon\n\
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c# try to switch to cpu number h (in hex)\n"
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c# try to switch to cpu number h (in hex)\n\
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c# $ run command '$' (one of 'r','S' or 't') on all cpus in xmon\n"
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#endif
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"\
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C checksum\n\
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@ -644,7 +654,12 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
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spin_cpu_relax();
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touch_nmi_watchdog();
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} else {
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if (!locked_down)
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cmd = 1;
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#ifdef CONFIG_SMP
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if (xmon_batch)
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cmd = batch_cmds(regs);
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#endif
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if (!locked_down && cmd)
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cmd = cmds(regs);
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if (locked_down || cmd != 0) {
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/* exiting xmon */
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@ -1243,11 +1258,112 @@ static void bootcmds(void)
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}
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}
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#ifdef CONFIG_SMP
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static int xmon_switch_cpu(unsigned long cpu)
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{
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int timeout;
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xmon_taken = 0;
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mb();
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xmon_owner = cpu;
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timeout = 10000000;
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while (!xmon_taken) {
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if (--timeout == 0) {
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if (test_and_set_bit(0, &xmon_taken))
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break;
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/* take control back */
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mb();
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xmon_owner = smp_processor_id();
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printf("cpu 0x%lx didn't take control\n", cpu);
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return 0;
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}
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barrier();
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}
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return 1;
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}
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static int xmon_batch_next_cpu(void)
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{
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unsigned long cpu;
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while (!cpumask_empty(&xmon_batch_cpus)) {
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cpu = cpumask_next_wrap(smp_processor_id(), &xmon_batch_cpus,
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xmon_batch_start_cpu, true);
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if (cpu == nr_cpumask_bits)
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break;
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if (xmon_batch_start_cpu == -1)
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xmon_batch_start_cpu = cpu;
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if (xmon_switch_cpu(cpu))
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return 0;
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cpumask_clear_cpu(cpu, &xmon_batch_cpus);
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}
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xmon_batch = 0;
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printf("%x:mon> \n", smp_processor_id());
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return 1;
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}
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static int batch_cmds(struct pt_regs *excp)
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{
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int cmd;
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/* simulate command entry */
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cmd = xmon_batch;
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termch = '\n';
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last_cmd = NULL;
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xmon_regs = excp;
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printf("%x:", smp_processor_id());
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printf("mon> ");
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printf("%c\n", (char)cmd);
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switch (cmd) {
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case 'r':
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prregs(excp); /* print regs */
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break;
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case 'S':
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super_regs();
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break;
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case 't':
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backtrace(excp);
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break;
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}
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cpumask_clear_cpu(smp_processor_id(), &xmon_batch_cpus);
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return xmon_batch_next_cpu();
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}
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static int cpu_cmd(void)
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{
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#ifdef CONFIG_SMP
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unsigned long cpu, first_cpu, last_cpu;
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int timeout;
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cpu = skipbl();
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if (cpu == '#') {
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xmon_batch = skipbl();
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if (xmon_batch) {
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switch (xmon_batch) {
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case 'r':
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case 'S':
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case 't':
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cpumask_copy(&xmon_batch_cpus, &cpus_in_xmon);
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if (cpumask_weight(&xmon_batch_cpus) <= 1) {
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printf("There are no other cpus in xmon\n");
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break;
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}
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xmon_batch_start_cpu = -1;
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if (!xmon_batch_next_cpu())
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return 1;
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break;
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default:
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printf("c# only supports 'r', 'S' and 't' commands\n");
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}
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xmon_batch = 0;
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return 0;
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}
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}
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termch = cpu;
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if (!scanhex(&cpu)) {
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/* print cpus waiting or in xmon */
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@ -1279,27 +1395,15 @@ static int cpu_cmd(void)
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#endif
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return 0;
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}
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xmon_taken = 0;
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mb();
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xmon_owner = cpu;
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timeout = 10000000;
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while (!xmon_taken) {
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if (--timeout == 0) {
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if (test_and_set_bit(0, &xmon_taken))
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break;
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/* take control back */
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mb();
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xmon_owner = smp_processor_id();
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printf("cpu 0x%lx didn't take control\n", cpu);
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return 0;
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}
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barrier();
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}
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return 1;
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#else
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return 0;
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#endif /* CONFIG_SMP */
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return xmon_switch_cpu(cpu);
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}
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#else
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static int cpu_cmd(void)
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{
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return 0;
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}
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#endif /* CONFIG_SMP */
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static unsigned short fcstab[256] = {
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0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
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