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:
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@xxxxxxx>
--- 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.
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@xxxxxxxxxxxxx>
> ---
> 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;
> }
>
--
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