From: Stephen Brennan <stephen.s.brennan@oracle.com>
To: Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
John Ogness <john.ogness@linutronix.de>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 4/4] printk: Drop console_sem during panic
Date: Fri, 21 Jan 2022 11:02:22 -0800 [thread overview]
Message-ID: <20220121190222.572694-5-stephen.s.brennan@oracle.com> (raw)
In-Reply-To: <20220121190222.572694-1-stephen.s.brennan@oracle.com>
If another CPU is in panic, we are about to be halted. Try to gracefully
drop console_sem and allow the panic CPU to grab it easily.
Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
---
kernel/printk/printk.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ca253ac07615..c2dc8ebd9509 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2668,7 +2668,7 @@ void console_unlock(void)
for (;;) {
size_t ext_len = 0;
- int handover;
+ int handover, pcpu;
size_t len;
skip:
@@ -2739,6 +2739,12 @@ void console_unlock(void)
if (handover)
return;
+ /* Allow panic_cpu to take over the consoles safely */
+ pcpu = atomic_read(&panic_cpu);
+ if (unlikely(pcpu != PANIC_CPU_INVALID &&
+ pcpu != raw_smp_processor_id()))
+ break;
+
if (do_cond_resched)
cond_resched();
}
--
2.30.2
next prev parent reply other threads:[~2022-01-21 19:03 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-21 19:02 [PATCH 0/4] printk: reduce deadlocks during panic Stephen Brennan
2022-01-21 19:02 ` [PATCH 1/4] panic: Add panic_in_progress helper Stephen Brennan
2022-01-25 11:48 ` Petr Mladek
2022-01-26 17:37 ` Stephen Brennan
2022-01-21 19:02 ` [PATCH 2/4] printk: disable optimistic spin during panic Stephen Brennan
2022-01-25 12:42 ` Petr Mladek
2022-01-26 9:18 ` Sergey Senozhatsky
2022-01-26 9:45 ` John Ogness
2022-01-26 10:06 ` Sergey Senozhatsky
2022-01-26 18:15 ` Stephen Brennan
2022-01-27 7:11 ` Sergey Senozhatsky
2022-01-27 9:09 ` John Ogness
2022-01-27 11:38 ` Petr Mladek
2022-01-27 12:43 ` John Ogness
2022-01-27 14:25 ` Petr Mladek
2022-01-21 19:02 ` [PATCH 3/4] printk: Avoid livelock with heavy printk " Stephen Brennan
2022-01-25 14:25 ` Petr Mladek
2022-01-21 19:02 ` Stephen Brennan [this message]
2022-01-24 16:12 ` [PATCH 4/4] printk: Drop console_sem " John Ogness
2022-01-24 16:26 ` John Ogness
2022-01-25 15:04 ` Petr Mladek
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