From 1fb8915b9876a80f43732980208b39d013f8da9d Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Thu, 11 Dec 2014 09:12:01 -0500 Subject: [PATCH] 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 Signed-off-by: Steven Rostedt --- kernel/printk/printk.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 5af2b8bc88f0..9b896e7a50a9 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -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; -- 2.20.1