linux-kernel - [RFC][PATCH -next 0/2] cond_resched() some of console

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Date:	Thu, 14 Jan 2016 13:57:21 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Tejun Heo <tj@...nel.org>, Jan Kara <jack@...e.com>,
	Petr Mladek <pmladek@...e.com>,
	Kyle McMartin <kyle@...nel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Calvin Owens <calvinowens@...com>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: [RFC][PATCH -next 0/2] cond_resched() some of console_trylock callers

Hello,

RFC (apologies for sending it during the merge window. no rush)

console_unlock() allows to cond_resched() if its caller has
set `console_may_schedule' to 1 (this functionality present
since commit '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()) are
not necessarily executing in atomic contexts, and some of them
can cond_resched() in console_unlock(). So console_trylock()
can set `console_may_schedule' to 0 only if cond_resched() is
invalid in the current context, and set it to 1 otherwise.

Patch 0001 addresses a theoretical loss of printk messages and,
at the same time, serves as a preparation work for 0002.

Sergey Senozhatsky (2):
  printk: move can_use_console out of console_trylock_for_printk
  printk: set may_schedule for some of console_trylock callers

 kernel/printk/printk.c | 84 ++++++++++++++++++++++++--------------------------
 1 file changed, 40 insertions(+), 44 deletions(-)

-- 
2.7.0