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,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>
Subject: [PATCH v2 13/13] panic: Fixes the panic_print NMI backtrace setting
Date: Tue, 19 Jul 2022 16:53:26 -0300 [thread overview]
Message-ID: <20220719195325.402745-14-gpiccoli@igalia.com> (raw)
In-Reply-To: <20220719195325.402745-1-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>
---
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 a3308af28a21..7fb604e95ef9 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
--
2.37.1
prev parent reply other threads:[~2022-07-19 19:59 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-19 19:53 [PATCH v2 00/13] The panic notifiers refactor strikes back - fixes/clean-ups Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 01/13] ARM: Disable FIQs (but not IRQs) on CPUs shutdown paths Guilherme G. Piccoli
2022-08-07 15:35 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 02/13] notifier: Add panic notifiers info and purge trailing whitespaces Guilherme G. Piccoli
2022-08-03 9:21 ` Baoquan He
2022-07-19 19:53 ` [PATCH v2 03/13] firmware: google: Test spinlock on panic path to avoid lockups Guilherme G. Piccoli
2022-08-07 15:38 ` Guilherme G. Piccoli
2022-08-08 5:07 ` Evan Green
2022-08-08 15:14 ` Guilherme G. Piccoli
2022-08-08 15:26 ` Greg Kroah-Hartman
2022-08-08 15:37 ` Guilherme G. Piccoli
2022-08-10 12:54 ` Greg Kroah-Hartman
2022-07-19 19:53 ` [PATCH v2 04/13] soc: bcm: brcmstb: Document panic notifier action and remove useless header Guilherme G. Piccoli
2022-07-20 23:00 ` Florian Fainelli
2022-07-21 13:17 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 05/13] alpha: Clean-up the panic notifier code Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 06/13] um: Improve panic notifiers consistency and ordering Guilherme G. Piccoli
2022-08-07 15:40 ` Guilherme G. Piccoli
2022-08-09 18:09 ` Johannes Berg
2022-08-09 19:03 ` Guilherme G. Piccoli
2022-08-09 19:08 ` Johannes Berg
2022-08-09 19:45 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 07/13] parisc: Replace regular spinlock with spin_trylock on panic path Guilherme G. Piccoli
2022-07-20 1:43 ` Jeroen Roovers
2022-07-21 13:19 ` Guilherme G. Piccoli
2022-07-21 13:45 ` Helge Deller
2022-07-21 14:00 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 08/13] tracing: Improve panic/die notifiers Guilherme G. Piccoli
2022-08-03 9:36 ` Baoquan He
2022-08-03 9:52 ` Baoquan He
2022-08-03 11:44 ` Guilherme G. Piccoli
2022-08-07 15:46 ` Guilherme G. Piccoli
2022-08-16 14:14 ` Steven Rostedt
2022-08-16 14:57 ` Alan Stern
2022-08-16 15:52 ` Steven Rostedt
2022-08-16 20:12 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 09/13] notifier: Show function names on notifier routines if DEBUG_NOTIFIERS is set Guilherme G. Piccoli
2022-07-19 20:33 ` Arjan van de Ven
2022-07-19 20:44 ` Guilherme G. Piccoli
2022-07-19 20:48 ` Arjan van de Ven
2022-07-19 21:00 ` Guilherme G. Piccoli
2022-07-19 22:04 ` Arjan van de Ven
2022-07-21 13:20 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 10/13] EDAC/altera: Skip the panic notifier if kdump is loaded Guilherme G. Piccoli
2022-08-07 15:48 ` Guilherme G. Piccoli
2022-08-16 18:44 ` Dinh Nguyen
2022-08-16 20:16 ` Guilherme G. Piccoli
2022-08-17 17:31 ` Borislav Petkov
2022-08-17 18:45 ` Guilherme G. Piccoli
2022-08-17 19:34 ` Borislav Petkov
2022-08-17 20:28 ` Guilherme G. Piccoli
2022-08-17 21:02 ` Borislav Petkov
2022-08-17 21:39 ` Guilherme G. Piccoli
2022-08-17 21:46 ` Borislav Petkov
2022-08-17 21:56 ` Guilherme G. Piccoli
2022-08-17 22:00 ` Borislav Petkov
2022-08-17 22:09 ` Guilherme G. Piccoli
2022-08-17 22:19 ` Borislav Petkov
2022-08-17 22:49 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 11/13] video/hyperv_fb: Avoid taking busy spinlock on panic path Guilherme G. Piccoli
2022-07-25 18:09 ` Michael Kelley (LINUX)
2022-07-25 22:05 ` Guilherme G. Piccoli
2022-07-19 19:53 ` [PATCH v2 12/13] drivers/hv/vmbus, video/hyperv_fb: Untangle and refactor Hyper-V panic notifiers Guilherme G. Piccoli
2022-07-25 18:55 ` Michael Kelley (LINUX)
2022-07-19 19:53 ` Guilherme G. Piccoli [this message]
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