console: introduce wrappers to read/write console flags

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After switching to SRCU for console list iteration, some readers
will begin readings console->flags as a data race. Locklessly
reading console->flags provides a consistent value because there
is at most one CPU modifying console->flags and that CPU is
using only read-modify-write operations.

Introduce a wrapper for SRCU iterators to read console flags.
Introduce a matching wrapper to write to flags of registered
consoles. Writing to flags of registered consoles is synchronized
by the console_list_lock.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20221116162152.193147-13-john.ogness@linutronix.de

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John Ogness 2022-11-16 17:27:24 +01:06 • committed by Petr Mladek

parent 4dc64682ad

commit 100bdef2c1

2 changed files with 50 additions and 5 deletions

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45

include/linux/console.h

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10

kernel/printk/printk.c

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