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linux-stable/kernel/printk
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Maninder Singh 375899cddc printk: make sure to print log on console. 
This patch make sure printing of log on console if loglevel
at time of storing log is less than current console loglevel.

@why
In SMP printk can work asynchronously, logs can be missed on console
because it checks current log level at time of console_unlock,
not at time of storing logs.

func()
{
....
....
        console_verbose();  // user wants to have all the logs on console.
        pr_alert();
	dump_backtrace(); //prints with default loglevel.
        ...
        console_silent(); // stop all logs from printing on console.
}

Now if console_lock was owned by another process, the messages might
be handled after the consoles were silenced.

Reused flag LOG_NOCONS as its usage is gone long back by the commit
5c2992ee7f ("printk: remove console flushing special cases
for partial buffered lines").

Note that there are still some corner cases where this patch is not enough.
For example, when the messages are flushed later from printk_safe buffers
or when there are races between console_verbose() and console_silent()
callers.

Link: http://lkml.kernel.org/r/20180601090029epcas5p3cc93d4bfbebb3199f0a2684058da7e26~z-a_jkmrI2993329933epcas5p3q@epcas5p3.samsung.com
Cc: linux-kernel@vger.kernel.org
Cc: a.sahrawat@samsung.com
Cc: pankaj.m@samsung.com
Cc: v.narang@samsung.com
Cc: <maninder1.s@samsung.com>
Signed-off-by: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2018-06-27 16:14:28 +02:00
..
braille.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
braille.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
console_cmdline.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
internal.h printk: Use the main logbuf in NMI when logbuf_lock is available 2017-05-19 14:42:19 +02:00
Makefile printk: introduce per-cpu safe_print seq buffer 2017-02-08 11:07:11 +01:00
printk.c printk: make sure to print log on console. 2018-06-27 16:14:28 +02:00
printk_safe.c printk: drop in_nmi check from printk_safe_flush_on_panic() 2018-06-05 13:38:15 +02:00