linux-kernel - [PATCH] pstore: Fix printing of duplicate boot messages to console

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Date:   Thu, 23 Jan 2020 21:30:31 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Kees Cook <keescook@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Joel Fernandes <joel@...lfernandes.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Subject: [PATCH] pstore: Fix printing of duplicate boot messages to console

Since commit f92b070f2dc8 ("printk: Do not miss new messages
when replaying the log"), CON_PRINTBUFFER flag causes the
duplicate boot messages to be printed on the console when
PSTORE_CONSOLE and earlycon (boot console) is enabled.
Pstore console registers to boot console when earlycon is
enabled during pstore_register_console as a part of ramoops
initialization in postcore_initcall and the printk core
checks for CON_PRINTBUFFER flag and replays the log buffer
to registered console (in this case pstore console which
just registered to boot console) causing duplicate messages
to be printed. Remove the CON_PRINTBUFFER flag from pstore
console since pstore is not concerned with the printing of
buffer to console but with writing of the buffer to the
backend.

Console log with earlycon and pstore console enabled:

[    0.008342] Console: colour dummy device 80x25
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x51df805e]
...
[    1.244049] hw-breakpoint: found 6 breakpoint and 4 watchpoint registers.
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x51df805e]

Fixes: f92b070f2dc8 ("printk: Do not miss new messages when replaying the log")
Reported-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
---
 fs/pstore/platform.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index d896457e7c11..271b00db0973 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -505,7 +505,7 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 static struct console pstore_console = {
 	.name	= "pstore",
 	.write	= pstore_console_write,
-	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
+	.flags	= CON_ENABLED | CON_ANYTIME,
 	.index	= -1,
 };

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