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kdb: Do not assume write() callback available

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commit 6d3e0d8cc6 upstream.

It is allowed for consoles to not provide a write() callback. For
example ttynull does this.

Check if a write() callback is available before using it.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20230717194607.145135-2-john.ogness@linutronix.de
Cc: Brian Norris <briannorris@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
John Ogness 2023-07-17 21:52:01 +02:06 committed by Greg Kroah-Hartman
parent 22e19c8c5f
commit 9c0a3aab4b
1 changed files with 2 additions and 0 deletions
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2
kernel/debug/kdb/kdb_io.c
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@ -577,6 +577,8 @@ static void kdb_msg_write(const char *msg, int msg_len)
continue;
if (c == dbg_io_ops->cons)
continue;
if (!c->write)
continue;
/*
* Set oops_in_progress to encourage the console drivers to
* disregard their internal spin locks: in the current calling