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author | Sergey Senozhatsky <sergey.senozhatsky@gmail.com> | 2016-03-18 00:21:23 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-03-18 01:09:34 +0300 |
commit | 6b97a20d3a7909daa06625d4440c2c52d7bf08d7 (patch) | |
tree | aa794a72f34aceddfaacea169feec753460ab889 /Documentation/kdump | |
parent | a8199371afc27946d72f0d53e938e78d2ea0bae3 (diff) | |
download | linux-6b97a20d3a7909daa06625d4440c2c52d7bf08d7.tar.xz |
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 8d91f8b15361 ("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: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Petr 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/kdump')
0 files changed, 0 insertions, 0 deletions