From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Petr Mladek <pmladek@suse.com>, Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: [PATCH 2/2] printk: wake up klogd in vprintk_emit
Date: Sat, 14 Apr 2018 12:01:45 +0900 [thread overview]
Message-ID: <20180414030145.26304-1-sergey.senozhatsky@gmail.com> (raw)
We wake up klogd very late - only when current console_sem owner
is done pushing pending kernel messages to the serial/net consoles.
In some cases this results in lost syslog messages, because kernel
log buffer is a circular buffer and if we don't wakeup syslog long
enough there are chances that logbuf simply will wrap around.
The patch moves the klog wake up call to vprintk_emit(), which is
the only legit way for a kernel message to appear in the logbuf,
right before we attempt to grab the console_sem (possibly spinning
on it waiting for the hand off) and call console drivers.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
kernel/printk/printk.c | 14 ++------------
1 file changed, 2 insertions(+), 12 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 2f4af216bd6e..86f0b337cbf6 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1888,6 +1888,7 @@ asmlinkage int vprintk_emit(int facility, int level,
printed_len = log_output(facility, level, lflags, dict, dictlen, text, text_len);
+ wake_up_klogd();
logbuf_unlock_irqrestore(flags);
/* If called from the scheduler, we can not call up(). */
@@ -2289,9 +2290,7 @@ void console_unlock(void)
{
static char ext_text[CONSOLE_EXT_LOG_MAX];
static char text[LOG_LINE_MAX + PREFIX_MAX];
- static u64 seen_seq;
unsigned long flags;
- bool wake_klogd = false;
bool do_cond_resched, retry;
if (console_suspended) {
@@ -2335,11 +2334,6 @@ void console_unlock(void)
printk_safe_enter_irqsave(flags);
raw_spin_lock(&logbuf_lock);
- if (seen_seq != log_next_seq) {
- wake_klogd = true;
- seen_seq = log_next_seq;
- }
-
if (console_seq < log_first_seq) {
len = sprintf(text, "** %u printk messages dropped **\n",
(unsigned)(log_first_seq - console_seq));
@@ -2397,7 +2391,7 @@ void console_unlock(void)
if (console_lock_spinning_disable_and_check()) {
printk_safe_exit_irqrestore(flags);
- goto out;
+ return;
}
printk_safe_exit_irqrestore(flags);
@@ -2429,10 +2423,6 @@ void console_unlock(void)
if (retry && console_trylock())
goto again;
-
-out:
- if (wake_klogd)
- wake_up_klogd();
}
EXPORT_SYMBOL(console_unlock);
--
2.17.0
next reply other threads:[~2018-04-14 3:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-14 3:01 Sergey Senozhatsky [this message]
2018-04-18 14:04 ` [PATCH 2/2] printk: wake up klogd in vprintk_emit Petr Mladek
2018-04-19 1:23 ` Sergey Senozhatsky
2018-04-19 9:54 ` Petr Mladek
2018-04-18 14:29 ` Steven Rostedt
2018-04-18 15:02 ` Petr Mladek
2018-04-18 15:10 ` Steven Rostedt
2018-04-19 1:17 ` Sergey Senozhatsky
2018-04-19 1:42 ` [PATCHv2] " Sergey Senozhatsky
2018-04-19 10:02 ` Petr Mladek
2018-04-20 1:52 ` Sergey Senozhatsky
2018-04-20 8:18 ` Petr Mladek
2018-04-25 13:23 ` Petr Mladek
2018-04-26 1:44 ` Sergey Senozhatsky
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