From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Changbin Du <changbin.du@gmail.com>
Cc: Jiri Slaby <jirislaby@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
Subject: Re: [PATCH] sysrq: do not omit current cpu when showing backtrace of all active CPUs
Date: Mon, 17 Jan 2022 16:50:21 +0100 [thread overview]
Message-ID: <YeWQPVy30EFTQaoq@kroah.com> (raw)
In-Reply-To: <20220117154300.2808-1-changbin.du@gmail.com>
On Mon, Jan 17, 2022 at 11:43:00PM +0800, Changbin Du wrote:
> The backtrace of current CPU also should be printed as it is active. This
> change add stack trace for current CPU and print a hint for idle CPU for
> the generic workqueue based printing. (x86 already does this)
How does x86 already do this? What processors do not currently do this?
> Now it looks like below:
> [ 279.401567] sysrq: Show backtrace of all active CPUs
> [ 279.407234] sysrq: CPU5:
> [ 279.407505] Call Trace:
> [ 279.408789] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
> [ 279.411698] [<ffffffff800060ac>] show_stack+0x32/0x3e
> [ 279.411809] [<ffffffff80542258>] sysrq_handle_showallcpus+0x4c/0xc6
> [ 279.411929] [<ffffffff80542f16>] __handle_sysrq+0x106/0x26c
> [ 279.412034] [<ffffffff805436a8>] write_sysrq_trigger+0x64/0x74
> [ 279.412139] [<ffffffff8029cd48>] proc_reg_write+0x8e/0xe2
> [ 279.412252] [<ffffffff8021a8f8>] vfs_write+0x90/0x2be
> [ 279.412362] [<ffffffff8021acd2>] ksys_write+0xa6/0xce
> [ 279.412467] [<ffffffff8021ad24>] sys_write+0x2a/0x38
> [ 279.412689] [<ffffffff80003ff8>] ret_from_syscall+0x0/0x2
> [ 279.417173] sysrq: CPU6: backtrace skipped as idling
> [ 279.417185] sysrq: CPU4: backtrace skipped as idling
> [ 279.417187] sysrq: CPU0: backtrace skipped as idling
> [ 279.417181] sysrq: CPU7: backtrace skipped as idling
> [ 279.417190] sysrq: CPU1: backtrace skipped as idling
> [ 279.417193] sysrq: CPU3: backtrace skipped as idling
> [ 279.417219] sysrq: CPU2:
> [ 279.419179] Call Trace:
> [ 279.419440] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
> [ 279.419782] [<ffffffff800060ac>] show_stack+0x32/0x3e
> [ 279.420015] [<ffffffff80542b30>] showacpu+0x5c/0x96
> [ 279.420317] [<ffffffff800ba71c>] flush_smp_call_function_queue+0xd6/0x218
> [ 279.420569] [<ffffffff800bb438>] generic_smp_call_function_single_interrupt+0x14/0x1c
> [ 279.420798] [<ffffffff800079ae>] handle_IPI+0xaa/0x13a
> [ 279.421024] [<ffffffff804dcb92>] riscv_intc_irq+0x56/0x70
> [ 279.421274] [<ffffffff80a05b70>] generic_handle_arch_irq+0x6a/0xfa
> [ 279.421518] [<ffffffff80004006>] ret_from_exception+0x0/0x10
> [ 279.421750] [<ffffffff80096492>] rcu_idle_enter+0x16/0x1e
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
> drivers/tty/sysrq.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index bbfd004449b5..34cfdda4aff5 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -232,8 +232,10 @@ static void showacpu(void *dummy)
> unsigned long flags;
>
> /* Idle CPUs have no interesting backtrace. */
> - if (idle_cpu(smp_processor_id()))
> + if (idle_cpu(smp_processor_id())) {
> + pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
> return;
> + }
Why do you need to see the skipped processor? Can't you just infer this
from a lack of calltrace on the other cpus? What needs to see this
information?
>
> raw_spin_lock_irqsave(&show_lock, flags);
> pr_info("CPU%d:\n", smp_processor_id());
> @@ -260,10 +262,13 @@ static void sysrq_handle_showallcpus(int key)
>
> if (in_hardirq())
> regs = get_irq_regs();
> - if (regs) {
> - pr_info("CPU%d:\n", smp_processor_id());
> +
> + pr_info("CPU%d:\n", smp_processor_id());
> + if (regs)
> show_regs(regs);
> - }
> + else
> + show_stack(NULL, NULL, KERN_INFO);
> +
Why is this change needed as well?
thanks,
greg k-h
next prev parent reply other threads:[~2022-01-17 15:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-17 15:43 [PATCH] sysrq: do not omit current cpu when showing backtrace of all active CPUs Changbin Du
2022-01-17 15:50 ` Greg Kroah-Hartman [this message]
2022-01-18 0:33 ` Changbin Du
2022-04-26 11:24 ` Greg Kroah-Hartman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YeWQPVy30EFTQaoq@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=changbin.du@gmail.com \
--cc=jirislaby@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=palmer@dabbelt.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox