2:23 a.m.
On 2022/05/13 16:03, 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 parameter 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.
Good, I think that the option will be sometimes useful and the code
looks good to me.
Could you add a help text?
And I think that the option works only for dumpfiles captured by kdump,
in other words, does not work for qemu live dumps, ramdumps etc. So
could you mention it in the help text and commit log?
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(a)bytedance.com>
> ---
> defs.h | 1 +
> kernel.c | 11 ++++++++++-
> x86_64.c | 8 ++++++++
> 3 files changed, 19 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/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;
> }
>