linux-kernel - [RFC] softlockup: serialized softlockup's log

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 14 Nov 2023 10:15:29 +0800
From:   lizhe.67@...edance.com
To:     akpm@...ux-foundation.org, dianders@...omium.org, pmladek@...e.com,
        kernelfans@...il.com, lecopzer.chen@...iatek.com
Cc:     linux-kernel@...r.kernel.org, lizefan.x@...edance.com,
        lizhe.67@...edance.com
Subject: [RFC] softlockup: serialized softlockup's log

From: Li Zhe <lizhe.67@...edance.com>

If multiple CPUs trigger softlockup at the same time, the softlockup's
logs will appear staggeredly in dmesg, which will affect the viewing of
the logs for developer. Since the code path for outputting softlockup logs
is not a kernel hotspot and the performance requirements for the code
are not strict, locks are used to serialize the softlockup log output
to improve the readability of the logs.

Signed-off-by: Li Zhe <lizhe.67@...edance.com>
---
 kernel/watchdog.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 5cd6d4e26915..8324ac194d0a 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -448,6 +448,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 	struct pt_regs *regs = get_irq_regs();
 	int duration;
 	int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
+	static DEFINE_SPINLOCK(watchdog_timer_lock);
 
 	if (!watchdog_enabled)
 		return HRTIMER_NORESTART;
@@ -514,6 +515,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 		/* Start period for the next softlockup warning. */
 		update_report_ts();
 
+		spin_lock(&watchdog_timer_lock);
 		pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
 			smp_processor_id(), duration,
 			current->comm, task_pid_nr(current));
@@ -523,6 +525,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 			show_regs(regs);
 		else
 			dump_stack();
+		spin_unlock(&watchdog_timer_lock);
 
 		if (softlockup_all_cpu_backtrace) {
 			trigger_allbutcpu_cpu_backtrace(smp_processor_id());
-- 
2.20.1