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printk: Do not disable preemption for accessing printk_func 

As printk_func will either be the default function, or a per_cpu function
for the current CPU, there's no reason to disable preemption to access
it from printk. That's because if the printk_func is not the default
then the caller had better disabled preemption as they were the one to
change it.

Link: http://lkml.kernel.org/r/CA+55aFz5-_LKW4JHEBoWinN9_ouNcGRWAF2FUA35u46FRN-Kxw@mail.gmail.com

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
hifive-unleashed-5.1
Steven Rostedt (Red Hat) 2014-12-11 09:12:01 -05:00 committed by Steven Rostedt
parent db08655437
commit 1fb8915b98
1 changed files with 8 additions and 2 deletions
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10
kernel/printk/printk.c
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@ -1859,10 +1859,16 @@ asmlinkage __visible int printk(const char *fmt, ...)
int r;
va_start(args, fmt);
preempt_disable();
/*
* If a caller overrides the per_cpu printk_func, then it needs
* to disable preemption when calling printk(). Otherwise
* the printk_func should be set to the default. No need to
* disable preemption here.
*/
vprintk_func = this_cpu_read(printk_func);
r = vprintk_func(fmt, args);
preempt_enable();
va_end(args);
return r;