From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
To: akpm@linux-foundation.org, bhe@redhat.com, pmladek@suse.com,
kexec@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org,
netdev@vger.kernel.org, x86@kernel.org, kernel-dev@igalia.com,
kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com,
alejandro.j.jimenez@oracle.com,
andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de,
corbet@lwn.net, d.hatayama@jp.fujitsu.com,
dave.hansen@linux.intel.com, dyoung@redhat.com,
feng.tang@intel.com, gregkh@linuxfoundation.org,
mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com,
jgross@suse.com, john.ogness@linutronix.de,
keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org,
mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org,
rostedt@goodmis.org, senozhatsky@chromium.org,
stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com,
vkuznets@redhat.com, will@kernel.org, xuqiang36@huawei.com,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>
Subject: [PATCH V3 11/11] panic: Fixes the panic_print NMI backtrace setting
Date: Fri, 19 Aug 2022 19:17:31 -0300 [thread overview]
Message-ID: <20220819221731.480795-12-gpiccoli@igalia.com> (raw)
In-Reply-To: <20220819221731.480795-1-gpiccoli@igalia.com>
Commit 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print")
introduced a setting for the "panic_print" kernel parameter to allow
users to request a NMI backtrace on panic. Problem is that the panic_print
handling happens after the secondary CPUs are already disabled, hence
this option ended-up being kind of a no-op - kernel skips the NMI trace
in idling CPUs, which is the case of offline CPUs.
Fix it by checking the NMI backtrace bit in the panic_print prior to
the CPU disabling function.
Fixes: 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print")
Cc: Feng Tang <feng.tang@intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
V3:
- No changes.
V2:
- new patch, there was no V1 of this one.
Hi folks, thanks upfront for reviews. This is a new patch, fixing an issue
I found in my tests, so I shoved it into this fixes series.
Notice that while at it, I got rid of the "crash_kexec_post_notifiers"
local copy in panic(). This was introduced by commit b26e27ddfd2a
("kexec: use core_param for crash_kexec_post_notifiers boot option"),
but it is not clear from comments or commit message why this local copy
is required.
My understanding is that it's a mechanism to prevent some concurrency,
in case some other CPU modify this variable while panic() is running.
I find it very unlikely, hence I removed it - but if people consider
this copy needed, I can respin this patch and keep it, even providing a
comment about that, in order to be explict about its need.
Let me know your thoughts! Cheers,
Guilherme
kernel/panic.c | 47 +++++++++++++++++++++++++++--------------------
1 file changed, 27 insertions(+), 20 deletions(-)
diff --git a/kernel/panic.c b/kernel/panic.c
index c6eb8f8db0c0..b025a8f21c17 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -180,9 +180,6 @@ static void panic_print_sys_info(bool console_flush)
return;
}
- if (panic_print & PANIC_PRINT_ALL_CPU_BT)
- trigger_all_cpu_backtrace();
-
if (panic_print & PANIC_PRINT_TASK_INFO)
show_state();
@@ -199,6 +196,30 @@ static void panic_print_sys_info(bool console_flush)
ftrace_dump(DUMP_ALL);
}
+/*
+ * Helper that triggers the NMI backtrace (if set in panic_print)
+ * and then performs the secondary CPUs shutdown - we cannot have
+ * the NMI backtrace after the CPUs are off!
+ */
+static void panic_other_cpus_shutdown(void)
+{
+ if (panic_print & PANIC_PRINT_ALL_CPU_BT)
+ trigger_all_cpu_backtrace();
+
+ /*
+ * Note that smp_send_stop() is the usual SMP shutdown function,
+ * which unfortunately may not be hardened to work in a panic
+ * situation. If we want to do crash dump after notifier calls
+ * and kmsg_dump, we will need architecture dependent extra
+ * bits in addition to stopping other CPUs, hence we rely on
+ * crash_smp_send_stop() for that.
+ */
+ if (!crash_kexec_post_notifiers)
+ smp_send_stop();
+ else
+ crash_smp_send_stop();
+}
+
/**
* panic - halt the system
* @fmt: The text string to print
@@ -214,7 +235,6 @@ void panic(const char *fmt, ...)
long i, i_next = 0, len;
int state = 0;
int old_cpu, this_cpu;
- bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
if (panic_on_warn) {
/*
@@ -289,23 +309,10 @@ void panic(const char *fmt, ...)
*
* Bypass the panic_cpu check and call __crash_kexec directly.
*/
- if (!_crash_kexec_post_notifiers) {
+ if (!crash_kexec_post_notifiers)
__crash_kexec(NULL);
- /*
- * Note smp_send_stop is the usual smp shutdown function, which
- * unfortunately means it may not be hardened to work in a
- * panic situation.
- */
- smp_send_stop();
- } else {
- /*
- * If we want to do crash dump after notifier calls and
- * kmsg_dump, we will need architecture dependent extra
- * works in addition to stopping other CPUs.
- */
- crash_smp_send_stop();
- }
+ panic_other_cpus_shutdown();
/*
* Run any panic handlers, including those that might need to
@@ -326,7 +333,7 @@ void panic(const char *fmt, ...)
*
* Bypass the panic_cpu check and call __crash_kexec directly.
*/
- if (_crash_kexec_post_notifiers)
+ if (crash_kexec_post_notifiers)
__crash_kexec(NULL);
#ifdef CONFIG_VT
--
2.37.2
next prev parent reply other threads:[~2022-08-19 22:27 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-19 22:17 [PATCH V3 00/11] The panic notifiers refactor - fixes/clean-ups (V3) Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 01/11] ARM: Disable FIQs (but not IRQs) on CPUs shutdown paths Guilherme G. Piccoli
2022-09-18 13:58 ` Guilherme G. Piccoli
2022-10-17 14:00 ` Guilherme G. Piccoli
2022-10-17 14:17 ` Russell King (Oracle)
2022-10-17 14:50 ` Guilherme G. Piccoli
2022-10-17 17:47 ` Russell King (Oracle)
2022-10-17 19:43 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 02/11] notifier: Add panic notifiers info and purge trailing whitespaces Guilherme G. Piccoli
2022-11-22 13:19 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 03/11] alpha: Clean-up the panic notifier code Guilherme G. Piccoli
2022-11-22 13:22 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 04/11] um: Improve panic notifiers consistency and ordering Guilherme G. Piccoli
2022-09-18 14:00 ` Guilherme G. Piccoli
2022-09-18 21:19 ` Richard Weinberger
2022-09-19 11:44 ` Guilherme G. Piccoli
2022-10-17 14:01 ` Guilherme G. Piccoli
2022-10-17 14:10 ` Richard Weinberger
2022-10-17 14:22 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 05/11] parisc: Replace regular spinlock with spin_trylock on panic path Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 06/11] tracing: Improve panic/die notifiers Guilherme G. Piccoli
2022-09-18 14:04 ` Guilherme G. Piccoli
2022-10-17 14:02 ` Guilherme G. Piccoli
2022-10-20 21:29 ` Steven Rostedt
2022-10-20 21:53 ` Guilherme G. Piccoli
2022-10-20 22:22 ` Steven Rostedt
2022-10-20 22:37 ` Guilherme G. Piccoli
2022-11-22 13:27 ` Guilherme G. Piccoli
2022-12-13 23:51 ` Guilherme G. Piccoli
2022-12-14 0:06 ` Steven Rostedt
2022-12-14 0:52 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 07/11] notifiers: Add tracepoints to the notifiers infrastructure Guilherme G. Piccoli
2022-09-18 14:07 ` Guilherme G. Piccoli
2022-10-17 14:04 ` Guilherme G. Piccoli
2022-11-22 13:30 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 08/11] EDAC/altera: Skip the panic notifier if kdump is loaded Guilherme G. Piccoli
2022-09-18 14:10 ` Guilherme G. Piccoli
2022-10-17 14:05 ` Guilherme G. Piccoli
2022-11-22 13:33 ` Guilherme G. Piccoli
2022-11-22 15:06 ` Borislav Petkov
2023-02-10 16:01 ` Guilherme G. Piccoli
2022-12-09 16:03 ` Petr Mladek
2022-08-19 22:17 ` [PATCH V3 09/11] video/hyperv_fb: Avoid taking busy spinlock on panic path Guilherme G. Piccoli
2022-09-18 14:12 ` Guilherme G. Piccoli
2022-10-04 16:17 ` Michael Kelley (LINUX)
2022-08-19 22:17 ` [PATCH V3 10/11] drivers/hv/vmbus, video/hyperv_fb: Untangle and refactor Hyper-V panic notifiers Guilherme G. Piccoli
2022-10-04 16:24 ` Michael Kelley (LINUX)
2022-10-04 17:20 ` Guilherme G. Piccoli
2022-10-17 15:26 ` Michael Kelley (LINUX)
2022-11-10 21:32 ` Guilherme G. Piccoli
2022-11-11 22:47 ` Wei Liu
2022-11-11 23:16 ` Wei Liu
2022-11-12 21:53 ` Guilherme G. Piccoli
2022-08-19 22:17 ` Guilherme G. Piccoli [this message]
2022-09-18 14:13 ` [PATCH V3 11/11] panic: Fixes the panic_print NMI backtrace setting Guilherme G. Piccoli
2022-11-22 13:35 ` Guilherme G. Piccoli
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=20220819221731.480795-12-gpiccoli@igalia.com \
--to=gpiccoli@igalia.com \
--cc=akpm@linux-foundation.org \
--cc=alejandro.j.jimenez@oracle.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=arnd@arndb.de \
--cc=bhe@redhat.com \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=d.hatayama@jp.fujitsu.com \
--cc=dave.hansen@linux.intel.com \
--cc=dyoung@redhat.com \
--cc=fabiomirmar@gmail.com \
--cc=feng.tang@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=halves@canonical.com \
--cc=hidehiro.kawai.ez@hitachi.com \
--cc=jgross@suse.com \
--cc=john.ogness@linutronix.de \
--cc=keescook@chromium.org \
--cc=kernel-dev@igalia.com \
--cc=kernel@gpiccoli.net \
--cc=kexec@lists.infradead.org \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mhiramat@kernel.org \
--cc=mikelley@microsoft.com \
--cc=mingo@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=senozhatsky@chromium.org \
--cc=stern@rowland.harvard.edu \
--cc=tglx@linutronix.de \
--cc=vgoyal@redhat.com \
--cc=vkuznets@redhat.com \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=xuqiang36@huawei.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;
as well as URLs for NNTP newsgroup(s).