Re: [Crash-utility] [PATCH] Make bt -a accept a CPU as an argument

Currently 'bt -a' displays the stack traces of the active task on each CPU. This patch makes it possible to specify a CPU as an argument. Multiple CPU arguments may be specified. If no argument is given the default behaviour is maintained.

For example: Display the stack trace of the active task on CPU 0 and 1: crash> bt -a 0 1 PID: 0 TASK: ffffffff81a8d020 CPU: 0 COMMAND: "swapper" #0 [ffff880002207e90] crash_nmi_callback at ffffffff8102fee6 #1 [ffff880002207ea0] notifier_call_chain at ffffffff8152d525 #2 [ffff880002207ee0] atomic_notifier_call_chain at ffffffff8152d58a #3 [ffff880002207ef0] notify_die at ffffffff810a155e #4 [ffff880002207f20] do_nmi at ffffffff8152b1eb #5 [ffff880002207f50] nmi at ffffffff8152aab0 [exception RIP: native_safe_halt+0xb] RIP: ffffffff8103eacb RSP: ffffffff81a01ea8 RFLAGS: 00000296 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff81de5228 RBP: ffffffff81a01ea8 R8: 0000000000000000 R9: 0000000000000000 R10: 0012099429a6bea3 R11: 0000000000000000 R12: ffffffff81c066c0 R13: 0000000000000000 R14: ffffffffffffffff R15: ffffffff81de1000 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 --- <NMI exception stack> --- #6 [ffffffff81a01ea8] native_safe_halt at ffffffff8103eacb #7 [ffffffff81a01eb0] default_idle at ffffffff810167bd #8 [ffffffff81a01ed0] cpu_idle at ffffffff81009fc6 PID: 38 TASK: ffff88003eaae040 CPU: 1 COMMAND: "khungtaskd" #0 [ffff88003ad97ce8] machine_kexec at ffffffff81038f3b #1 [ffff88003ad97d48] crash_kexec at ffffffff810c5da2 #2 [ffff88003ad97e18] panic at ffffffff8152721a #3 [ffff88003ad97e98] watchdog at ffffffff810e6346 #4 [ffff88003ad97ee8] kthread at ffffffff8109af06 #5 [ffff88003ad97f48] kernel_thread at ffffffff8100c20a Signed-off-by: Aaron Tomlin <atomlin(a)redhat.com&gt; --- help.c | 37 ++++++++++++++++++++++++++++++++++--- kernel.c | 26 +++++++++++++++++++++++--- 2 files changed, 57 insertions(+), 6 deletions(-) diff --git a/help.c b/help.c index 91f22c3..62af23a 100644 --- a/help.c +++ b/help.c @@ -1704,11 +1704,13 @@ NULL char *help_bt[] = { "bt", "backtrace", -"[-a|-g|-r|-t|-T|-l|-e|-E|-f|-F|-o|-O] [-R ref] [-s [-x|d]] [-I ip] [-S sp]" +"[-a [cpu]|-g|-r|-t|-T|-l|-e|-E|-f|-F|-o|-O] [-R ref] [-s [-x|d]] [-I ip] [-S sp]" "\n [pid | task]", " Display a kernel stack backtrace. If no arguments are given, the stack", " trace of the current context will be displayed.\n", -" -a displays the stack traces of the active task on each CPU.", +" -a display the stack trace of the active task on a given CPU.", +" Multiple CPU arguments may be specified. If no arguments are given", +" the stack trace of the active task on each CPU is shown.", " (only applicable to crash dumps)", #ifdef GDB_5_3 " -g use gdb stack trace code. (alpha only)", @@ -1766,7 +1768,36 @@ char *help_bt[] = { " or display a stale frame reference. When in doubt as to the accuracy of a", " backtrace, the -t or -T options may help fill in the blanks.\n", "EXAMPLES", -" Display the stack trace of the active task(s) when the kernel panicked:\n", +" Display the stack trace of the active task on CPU 0 and 1:\n", +" %s> bt -a 0 1", +" PID: 0 TASK: ffffffff81a8d020 CPU: 0 COMMAND: \"swapper\"", +" #0 [ffff880002207e90] crash_nmi_callback at ffffffff8102fee6", +" #1 [ffff880002207ea0] notifier_call_chain at ffffffff8152d525", +" #2 [ffff880002207ee0] atomic_notifier_call_chain at ffffffff8152d58a", +" #3 [ffff880002207ef0] notify_die at ffffffff810a155e", +" #4 [ffff880002207f20] do_nmi at ffffffff8152b1eb", +" #5 [ffff880002207f50] nmi at ffffffff8152aab0", +" [exception RIP: native_safe_halt+0xb]", +" RIP: ffffffff8103eacb RSP: ffffffff81a01ea8 RFLAGS: 00000296", +" RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000", +" RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff81de5228", +" RBP: ffffffff81a01ea8 R8: 0000000000000000 R9: 0000000000000000", +" R10: 0012099429a6bea3 R11: 0000000000000000 R12: ffffffff81c066c0", +" R13: 0000000000000000 R14: ffffffffffffffff R15: ffffffff81de1000", +" ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018", +" --- <NMI exception stack> ---", +" #6 [ffffffff81a01ea8] native_safe_halt at ffffffff8103eacb", +" #7 [ffffffff81a01eb0] default_idle at ffffffff810167bd", +" #8 [ffffffff81a01ed0] cpu_idle at ffffffff81009fc6", +" ", +" PID: 38 TASK: ffff88003eaae040 CPU: 1 COMMAND: \"khungtaskd\"", +" #0 [ffff88003ad97ce8] machine_kexec at ffffffff81038f3b", +" #1 [ffff88003ad97d48] crash_kexec at ffffffff810c5da2", +" #2 [ffff88003ad97e18] panic at ffffffff8152721a", +" #3 [ffff88003ad97e98] watchdog at ffffffff810e6346", +" #4 [ffff88003ad97ee8] kthread at ffffffff8109af06", +" #5 [ffff88003ad97f48] kernel_thread at ffffffff8100c20a", +"\n Display the stack trace of the active task(s) when the kernel panicked:\n", " %s> bt -a", " PID: 286 TASK: c0b3a000 CPU: 0 COMMAND: \"in.rlogind\"", " #0 [c0b3be90] crash_save_current_state at c011aed0", diff --git a/kernel.c b/kernel.c index cdc53eb..6b3e25b 100644 --- a/kernel.c +++ b/kernel.c @@ -1972,15 +1972,15 @@ cmd_bt(void) int i, c; ulong value; struct task_context *tc; - int count, subsequent, active; + int count, subsequent, active, cpu; struct stack_hook hook; struct bt_info bt_info, bt_setup, *bt; struct reference reference; char *refptr; - ulong tgid; + ulong tgid, task; tc = NULL; - subsequent = active = count = 0; + subsequent = active = count = cpu = 0; hook.eip = hook.esp = 0; refptr = 0; bt = &bt_info; @@ -2232,6 +2232,26 @@ cmd_bt(void) error(FATAL, "-a option cannot be used with the -g option\n"); + while (args[optind]) { + cpu = dtoi(args[optind], FAULT_ON_ERROR, NULL); + if (cpu >= kt->cpus) { + error(FATAL, "invalid cpu number: system has only %d cpu%s\n", + kt->cpus, kt->cpus > 1 ? "s" : ""); + return; + } + if ((task = get_active_task(cpu))) + tc = task_to_context(task); + else { + error(FATAL, "cannot determine active task on cpu %ld\n", cpu); + return; + } + DO_TASK_BACKTRACE(); + + optind++; + if (!args[optind]) + return; + } + for (c = 0; c < NR_CPUS; c++) { if (setjmp(pc->foreach_loop_env)) { pc->flags &= ~IN_FOREACH; -- 1.9.0