Commit 8c4e93c3 authored by Petr Mladek's avatar Petr Mladek Committed by Thomas Gleixner
Browse files

printk: Prepare for nested printk_nmi_enter() 



There is plenty of space in the printk_context variable. Reserve one byte
there for the NMI context to be on the safe side.

It should never overflow. The BUG_ON(in_nmi() == NMI_MASK) in nmi_enter()
will trigger much earlier.

Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/20200505134100.681374113@linutronix.de
parent 1ed0948e

kernel/printk/internal.h

+5 −3
Original line number Diff line number Diff line
@@ -6,9 +6,11 @@ 


#ifdef CONFIG_PRINTK



#define PRINTK_SAFE_CONTEXT_MASK	 0x3fffffff

#define PRINTK_NMI_DIRECT_CONTEXT_MASK	 0x40000000

#define PRINTK_NMI_CONTEXT_MASK		 0x80000000

#define PRINTK_SAFE_CONTEXT_MASK	0x007ffffff

#define PRINTK_NMI_DIRECT_CONTEXT_MASK	0x008000000

#define PRINTK_NMI_CONTEXT_MASK		0xff0000000



#define PRINTK_NMI_CONTEXT_OFFSET	0x010000000



extern raw_spinlock_t logbuf_lock;

kernel/printk/printk_safe.c

+2 −2
Original line number Diff line number Diff line
@@ -295,12 +295,12 @@ static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args) 


void notrace printk_nmi_enter(void)

{

	this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);

	this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);

}



void notrace printk_nmi_exit(void)

{

	this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);

	this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);

}



/*

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