linux-kernel - [PATCH 2/2] watchdog: move softlockup_panic back to early

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Message-ID: <019420f881ee8e2582870c2770759954835adfad.1698441495.git.kjlx@templeofstupid.com>
Date:   Fri, 27 Oct 2023 14:46:53 -0700
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:     Douglas Anderson <dianders@...omium.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Arnd Bergmann <arnd@...db.de>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Hildenbrand <david@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pingfan Liu <kernelfans@...il.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "Guilherme G. Piccoli" <kernel@...ccoli.net>,
        Mike Rapoport <rppt@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 2/2] watchdog: move softlockup_panic back to early_param

Setting softlockup_panic from do_sysctl_args() causes it to take effect
later in boot.  The lockup detector is enabled before SMP is brought
online, but do_sysctl_args runs afterwards.  If a user wants to set
softlockup_panic on boot and have it trigger should a softlockup occur
during onlining of the non-boot processors, they could do this prior to
commit f117955a2255 ("kernel/watchdog.c: convert {soft/hard}lockup boot
parameters to sysctl aliases").  However, after this commit the value
of softlockup_panic is set too late to be of help for this type of
problem.  Restore the prior behavior.

Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
Cc: stable@...r.kernel.org
Fixes: f117955a2255 ("kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases")
---
 fs/proc/proc_sysctl.c | 1 -
 kernel/watchdog.c     | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 1c9635dddb70..de484195f49f 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1576,7 +1576,6 @@ static const struct sysctl_alias sysctl_aliases[] = {
 	{"hung_task_panic",			"kernel.hung_task_panic" },
 	{"numa_zonelist_order",			"vm.numa_zonelist_order" },
 	{"softlockup_all_cpu_backtrace",	"kernel.softlockup_all_cpu_backtrace" },
-	{"softlockup_panic",			"kernel.softlockup_panic" },
 	{ }
 };
 
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index d145305d95fe..5cd6d4e26915 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -283,6 +283,13 @@ static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 static unsigned long soft_lockup_nmi_warn;
 
+static int __init softlockup_panic_setup(char *str)
+{
+	softlockup_panic = simple_strtoul(str, NULL, 0);
+	return 1;
+}
+__setup("softlockup_panic=", softlockup_panic_setup);
+
 static int __init nowatchdog_setup(char *str)
 {
 	watchdog_user_enabled = 0;
-- 
2.25.1