[Crash-utility] [PATCH v2 1/2] bt: x86_64: filter out idle task stack
Qi Zheng
zhengqi.arch at bytedance.com
Fri May 20 02:47:18 UTC 2022
On 2022/5/20 10:26 AM, HAGIO KAZUHITO(萩尾 一仁) wrote:
> Hi Qi,
>
> thanks for the update.
>
> On 2022/05/19 22:48, Qi Zheng wrote:
>> When we use crash to troubleshoot softlockup and other problems,
>> we often use the 'bt -a' command to print the stacks of running
>> processes on all CPUs. But now some servers have hundreds of CPUs
>> (such as AMD machines), which causes the 'bt -a' command to output
>> a lot of process stacks. And many of these stacks are the stacks
>> of the idle process, which are not needed by us.
>>
>> Therefore, in order to reduce this part of the interference information,
>> this patch adds the -n option to the bt command. When we specify
>> '-n idle' (meaning no idle), the stack of the idle process will be
>> filtered out, thus speeding up our troubleshooting.
>>
>
>> And like option '-a' of bt, option '-n idle' works only for dumpfiles
>> captured by kdump.
>
> It's a bit different from '-a', will change to:
>
> And the option works only for crash dumps captured by kdump.
>
> because '-a' works for live dumps but '-n idle' doesn't work like this:
Got it.
>
> crash> bt -a -n idle
> PID: 0 TASK: ffffffff82212780 CPU: 0 COMMAND: "swapper/0"
> [exception RIP: native_safe_halt+2]
> RIP: ffffffff81820c92 RSP: ffffffff82203e90 RFLAGS: 00000246
> RAX: ffffffff818209c0 RBX: 0000000000000000 RCX: 0000000000000001
> RDX: 0000000000000001 RSI: 0000000000000087 RDI: 0000000000000000
> RBP: 0000000000000000 R8: 00007584cc726bcd R9: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 000000007f46e168 R15: 000000007ff922a0
> CS: 0010 SS: 0018
> #0 [ffffffff82203e90] default_idle at ffffffff818209da
> #1 [ffffffff82203eb0] do_idle at ffffffff810de691
> #2 [ffffffff82203ef0] cpu_startup_entry at ffffffff810de8ff
> #3 [ffffffff82203f10] start_kernel at ffffffff827821eb
> #4 [ffffffff82203f50] secondary_startup_64 at ffffffff810000e7
> ...
>
> And with the following patch,
>
> Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>
Thanks.
>
> --- a/help.c
> +++ b/help.c
> @@ -1909,7 +1909,7 @@ char *help_bt[] = {
> "bt",
> "backtrace",
> "[-a|-c cpu(s)|-g|-r|-t|-T|-l|-e|-E|-f|-F|-o|-O|-v|-p] [-R ref] [-s [-x|d]]"
> -"\n [-I ip] [-S sp] [pid | task]",
> +"\n [-I ip] [-S sp] [-n idle] [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.",
>
> No need to repost, we can fix these when merging.
Thank you very much! :)
>
> Thanks,
> Kazu
>
>>
>> The command output is as follows:
>> crash> bt -a -n idle
>> [...]
>> PID: 0 TASK: ffff889ff93f5a00 CPU: 5 COMMAND: "swapper/5"
>>
>> PID: 0 TASK: ffff889ff93f0000 CPU: 6 COMMAND: "swapper/6"
>>
>> PID: 0 TASK: ffff889ff8c30000 CPU: 7 COMMAND: "swapper/7"
>>
>> PID: 0 TASK: ffff889ff8c34380 CPU: 8 COMMAND: "swapper/8"
>>
>> PID: 0 TASK: ffff889ff8c32d00 CPU: 9 COMMAND: "swapper/9"
>>
>> PID: 0 TASK: ffff889ff8c31680 CPU: 10 COMMAND: "swapper/10"
>>
>> PID: 0 TASK: ffff889ff8c35a00 CPU: 11 COMMAND: "swapper/11"
>>
>> PID: 0 TASK: ffff889ff8c3c380 CPU: 12 COMMAND: "swapper/12"
>>
>> PID: 150773 TASK: ffff889fe85a1680 CPU: 13 COMMAND: "bash"
>> #0 [ffffc9000d35bcd0] machine_kexec at ffffffff8105a407
>> #1 [ffffc9000d35bd28] __crash_kexec at ffffffff8113033d
>> #2 [ffffc9000d35bdf0] panic at ffffffff81081930
>> #3 [ffffc9000d35be70] sysrq_handle_crash at ffffffff814e38d1
>> #4 [ffffc9000d35be78] __handle_sysrq.cold.12 at ffffffff814e4175
>> #5 [ffffc9000d35bea8] write_sysrq_trigger at ffffffff814e404b
>> #6 [ffffc9000d35beb8] proc_reg_write at ffffffff81330d86
>> #7 [ffffc9000d35bed0] vfs_write at ffffffff812a72d5
>> #8 [ffffc9000d35bf00] ksys_write at ffffffff812a7579
>> #9 [ffffc9000d35bf38] do_syscall_64 at ffffffff81004259
>> RIP: 00007fa7abcdc274 RSP: 00007fffa731f678 RFLAGS: 00000246
>> RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fa7abcdc274
>> RDX: 0000000000000002 RSI: 0000563ca51ee6d0 RDI: 0000000000000001
>> RBP: 0000563ca51ee6d0 R8: 000000000000000a R9: 00007fa7abd6be80
>> R10: 000000000000000a R11: 0000000000000246 R12: 00007fa7abdad760
>> R13: 0000000000000002 R14: 00007fa7abda8760 R15: 0000000000000002
>> ORIG_RAX: 0000000000000001 CS: 0033 SS: 002b
>> [...]
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch at bytedance.com>
>> ---
>> defs.h | 1 +
>> help.c | 30 ++++++++++++++++++++++++++++++
>> kernel.c | 11 ++++++++++-
>> x86_64.c | 8 ++++++++
>> 4 files changed, 49 insertions(+), 1 deletion(-)
>>
>> diff --git a/defs.h b/defs.h
>> index a6735d0..96a7429 100644
>> --- a/defs.h
>> +++ b/defs.h
>> @@ -5830,6 +5830,7 @@ ulong cpu_map_addr(const char *type);
>> #define BT_SHOW_ALL_REGS (0x2000000000000ULL)
>> #define BT_REGS_NOT_FOUND (0x4000000000000ULL)
>> #define BT_OVERFLOW_STACK (0x8000000000000ULL)
>> +#define BT_SKIP_IDLE (0x10000000000000ULL)
>> #define BT_SYMBOL_OFFSET (BT_SYMBOLIC_ARGS)
>>
>> #define BT_REF_HEXVAL (0x1)
>> diff --git a/help.c b/help.c
>> index 51a0fe3..6d8dc4f 100644
>> --- a/help.c
>> +++ b/help.c
>> @@ -1915,6 +1915,8 @@ char *help_bt[] = {
>> " -a displays the stack traces of the active task on each CPU.",
>> " (only applicable to crash dumps)",
>> " -A same as -a, but also displays vector registers (S390X only).",
>> +" -n idle filter the stack of idle tasks (x86_64).",
>> +" (only applicable to crash dumps)",
>> " -p display the stack trace of the panic task only.",
>> " (only applicable to crash dumps)",
>> " -c cpu display the stack trace of the active task on one or more CPUs,",
>> @@ -2004,6 +2006,34 @@ char *help_bt[] = {
>> " DS: 002b ESI: bfffc8a0 ES: 002b EDI: 00000000 ",
>> " SS: 002b ESP: bfffc82c EBP: bfffd224 ",
>> " CS: 0023 EIP: 400d032e ERR: 0000008e EFLAGS: 00000246 ",
>> +" ",
>> +" Display the stack trace of the active task(s) when the kernel panicked,",
>> +" and filter out the stack of the idle tasks:",
>> +" %s> bt -a -n idle",
>> +" [...]",
>> +" PID: 0 TASK: ffff889ff8c35a00 CPU: 11 COMMAND: \"swapper/11\"",
>> +" ",
>> +" PID: 0 TASK: ffff889ff8c3c380 CPU: 12 COMMAND: \"swapper/12\"",
>> +" ",
>> +" PID: 150773 TASK: ffff889fe85a1680 CPU: 13 COMMAND: \"bash\"",
>> +" #0 [ffffc9000d35bcd0] machine_kexec at ffffffff8105a407",
>> +" #1 [ffffc9000d35bd28] __crash_kexec at ffffffff8113033d",
>> +" #2 [ffffc9000d35bdf0] panic at ffffffff81081930",
>> +" #3 [ffffc9000d35be70] sysrq_handle_crash at ffffffff814e38d1",
>> +" #4 [ffffc9000d35be78] __handle_sysrq.cold.12 at ffffffff814e4175",
>> +" #5 [ffffc9000d35bea8] write_sysrq_trigger at ffffffff814e404b",
>> +" #6 [ffffc9000d35beb8] proc_reg_write at ffffffff81330d86",
>> +" #7 [ffffc9000d35bed0] vfs_write at ffffffff812a72d5",
>> +" #8 [ffffc9000d35bf00] ksys_write at ffffffff812a7579",
>> +" #9 [ffffc9000d35bf38] do_syscall_64 at ffffffff81004259",
>> +" RIP: 00007fa7abcdc274 RSP: 00007fffa731f678 RFLAGS: 00000246",
>> +" RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fa7abcdc274",
>> +" RDX: 0000000000000002 RSI: 0000563ca51ee6d0 RDI: 0000000000000001",
>> +" RBP: 0000563ca51ee6d0 R8: 000000000000000a R9: 00007fa7abd6be80",
>> +" R10: 000000000000000a R11: 0000000000000246 R12: 00007fa7abdad760",
>> +" R13: 0000000000000002 R14: 00007fa7abda8760 R15: 0000000000000002",
>> +" ORIG_RAX: 0000000000000001 CS: 0033 SS: 002b",
>> +" [...]",
>> "\n Display the stack trace of the active task on CPU 0 and 1:\n",
>> " %s> bt -c 0,1",
>> " PID: 0 TASK: ffffffff81a8d020 CPU: 0 COMMAND: \"swapper\"",
>> diff --git a/kernel.c b/kernel.c
>> index d0921cf..acfacaf 100644
>> --- a/kernel.c
>> +++ b/kernel.c
>> @@ -2503,7 +2503,7 @@ cmd_bt(void)
>> if (kt->flags & USE_OPT_BT)
>> bt->flags |= BT_OPT_BACK_TRACE;
>>
>> - while ((c = getopt(argcnt, args, "D:fFI:S:c:aAloreEgstTdxR:Ovp")) != EOF) {
>> + while ((c = getopt(argcnt, args, "D:fFI:S:c:n:aAloreEgstTdxR:Ovp")) != EOF) {
>> switch (c)
>> {
>> case 'f':
>> @@ -2672,6 +2672,11 @@ cmd_bt(void)
>> active++;
>> break;
>>
>> + case 'n':
>> + if (machine_type("X86_64") && STREQ(optarg, "idle"))
>> + bt->flags |= BT_SKIP_IDLE;
>> + break;
>> +
>> case 'r':
>> bt->flags |= BT_RAW;
>> break;
>> @@ -3092,6 +3097,10 @@ back_trace(struct bt_info *bt)
>> } else
>> machdep->get_stack_frame(bt, &eip, &esp);
>>
>> + /* skip idle task stack */
>> + if (bt->flags & BT_SKIP_IDLE)
>> + return;
>> +
>> if (bt->flags & BT_KSTACKP) {
>> bt->stkptr = esp;
>> return;
>> diff --git a/x86_64.c b/x86_64.c
>> index ecaefd2..cfafbcc 100644
>> --- a/x86_64.c
>> +++ b/x86_64.c
>> @@ -4918,6 +4918,9 @@ x86_64_get_stack_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
>> if (bt->flags & BT_DUMPFILE_SEARCH)
>> return x86_64_get_dumpfile_stack_frame(bt, pcp, spp);
>>
>> + if (bt->flags & BT_SKIP_IDLE)
>> + bt->flags &= ~BT_SKIP_IDLE;
>> +
>> if (pcp)
>> *pcp = x86_64_get_pc(bt);
>> if (spp)
>> @@ -4960,6 +4963,9 @@ x86_64_get_dumpfile_stack_frame(struct bt_info *bt_in, ulong *rip, ulong *rsp)
>> estack = -1;
>> panic = FALSE;
>>
>> + if (bt_in->flags & BT_SKIP_IDLE)
>> + bt_in->flags &= ~BT_SKIP_IDLE;
>> +
>> panic_task = tt->panic_task == bt->task ? TRUE : FALSE;
>>
>> if (panic_task && bt->machdep) {
>> @@ -5098,6 +5104,8 @@ next_sysrq:
>> if (!panic_task && STREQ(sym, "crash_nmi_callback")) {
>> *rip = *up;
>> *rsp = bt->stackbase + ((char *)(up) - bt->stackbuf);
>> + if ((bt->flags & BT_SKIP_IDLE) && is_idle_thread(bt->task))
>> + bt_in->flags |= BT_SKIP_IDLE;
>> return;
>> }
>>
--
Thanks,
Qi
More information about the Crash-utility
mailing list