printk: set may_schedule for some of console_trylock() callers
console_unlock() allows to cond_resched() if its caller has set `console_may_schedule' to 1, since 8d91f8b1 ("printk: do cond_resched() between lines while outputting to consoles"). The rules are: -- console_lock() always sets `console_may_schedule' to 1 -- console_trylock() always sets `console_may_schedule' to 0 However, console_trylock() callers (among them is printk()) do not always call printk() from atomic contexts, and some of them can cond_resched() in console_unlock(), so console_trylock() can set `console_may_schedule' to 1 for such processes. For !CONFIG_PREEMPT_COUNT kernels, however, console_trylock() always sets `console_may_schedule' to 0. It's possible to drop explicit preempt_disable()/preempt_enable() in vprintk_emit(), because console_unlock() and console_trylock() are now smart enough: a) console_unlock() does not cond_resched() when it's unsafe (console_trylock() takes care of that) b) console_unlock() does can_use_console() check. Signed-off-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: NPetr Mladek <pmladek@suse.com> Cc: Jan Kara <jack@suse.com> Cc: Tejun Heo <tj@kernel.org> Cc: Kyle McMartin <kyle@kernel.org> Cc: Dave Jones <davej@codemonkey.org.uk> Cc: Calvin Owens <calvinowens@fb.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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