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Date: Wed, 29 Mar 2017 18:25:06 +0900 From: Sergey Senozhatsky <sergey.senozhatsky@...il.com> To: Steven Rostedt <rostedt@...dmis.org>, Petr Mladek <pmladek@...e.com> Cc: Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, "Rafael J . Wysocki" <rjw@...ysocki.net>, Eric Biederman <ebiederm@...ssion.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.com>, Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>, linux-kernel@...r.kernel.org, Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>, Sergey Senozhatsky <sergey.senozhatsky@...il.com> Subject: [RFC][PATCHv2 3/8] printk: offload printing from wake_up_klogd_work_func() Offload printing of printk_deferred() messages from IRQ context to a schedulable printing kthread, when possible (the same way we do it in vprintk_emit()). Otherwise, console_unlock() can force the printing CPU to spend unbound amount of time flushing kernel messages from IRQ context. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com> --- kernel/printk/printk.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ab6b3b2a68c6..1927b5cb5cbe 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2741,8 +2741,16 @@ static void wake_up_klogd_work_func(struct irq_work *irq_work) * If trylock fails, someone else is doing the printing. * PRINTK_PENDING_OUTPUT bit is cleared by console_unlock(). */ - if (console_trylock()) - console_unlock(); + if (printk_kthread_enabled()) { + wake_up_process(printk_kthread); + } else { + /* + * If trylock fails, someone else is doing the + * printing + */ + if (console_trylock()) + console_unlock(); + } } if (test_and_clear_bit(PRINTK_PENDING_WAKEUP, &printk_pending)) -- 2.12.2
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