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Commit ab0f56b7 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Bernhard Thoben
Browse files

locking/refcounts: Include fewer headers in <linux/refcount.h> 



Debloat <linux/refcount.h>'s dependencies:

- <linux/kernel.h> is not needed, but <linux/compiler.h> is.
- <linux/mutex.h> is not needed, only a forward declaration of "struct mutex".
- <linux/spinlock.h> is not needed, <linux/spinlock_types.h> is enough.

Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/lkml/20180331220036.GA7676@avx2


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
(cherry picked from commit 75a040ff14d9a99fc041f5e1d8f09541cab13ba4)
parent aaab52ce

arch/x86/include/asm/refcount.h

0 → 100644
+110 −0
Original line number Diff line number Diff line 
#ifndef __ASM_X86_REFCOUNT_H

#define __ASM_X86_REFCOUNT_H

/*

 * x86-specific implementation of refcount_t. Based on PAX_REFCOUNT from

 * PaX/grsecurity.

 */

#include <linux/refcount.h>

#include <asm/bug.h>



/*

 * This is the first portion of the refcount error handling, which lives in

 * .text.unlikely, and is jumped to from the CPU flag check (in the

 * following macros). This saves the refcount value location into CX for

 * the exception handler to use (in mm/extable.c), and then triggers the

 * central refcount exception. The fixup address for the exception points

 * back to the regular execution flow in .text.

 */

#define _REFCOUNT_EXCEPTION				\

	".pushsection .text..refcount\n"		\

	"111:\tlea %[counter], %%" _ASM_CX "\n"		\

	"112:\t" ASM_UD2 "\n"				\

	ASM_UNREACHABLE					\

	".popsection\n"					\

	"113:\n"					\

	_ASM_EXTABLE_REFCOUNT(112b, 113b)



/* Trigger refcount exception if refcount result is negative. */

#define REFCOUNT_CHECK_LT_ZERO				\

	"js 111f\n\t"					\

	_REFCOUNT_EXCEPTION



/* Trigger refcount exception if refcount result is zero or negative. */

#define REFCOUNT_CHECK_LE_ZERO				\

	"jz 111f\n\t"					\

	REFCOUNT_CHECK_LT_ZERO



/* Trigger refcount exception unconditionally. */

#define REFCOUNT_ERROR					\

	"jmp 111f\n\t"					\

	_REFCOUNT_EXCEPTION



static __always_inline void refcount_add(unsigned int i, refcount_t *r)

{

	asm volatile(LOCK_PREFIX "addl %1,%0\n\t"

		REFCOUNT_CHECK_LT_ZERO

		: [counter] "+m" (r->refs.counter)

		: "ir" (i)

		: "cc", "cx");

}



static __always_inline void refcount_inc(refcount_t *r)

{

	asm volatile(LOCK_PREFIX "incl %0\n\t"

		REFCOUNT_CHECK_LT_ZERO

		: [counter] "+m" (r->refs.counter)

		: : "cc", "cx");

}



static __always_inline void refcount_dec(refcount_t *r)

{

	asm volatile(LOCK_PREFIX "decl %0\n\t"

		REFCOUNT_CHECK_LE_ZERO

		: [counter] "+m" (r->refs.counter)

		: : "cc", "cx");

}



static __always_inline __must_check

bool refcount_sub_and_test(unsigned int i, refcount_t *r)

{

	GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl", REFCOUNT_CHECK_LT_ZERO,

				  r->refs.counter, "er", i, "%0", e, "cx");

}



static __always_inline __must_check bool refcount_dec_and_test(refcount_t *r)

{

	GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl", REFCOUNT_CHECK_LT_ZERO,

				 r->refs.counter, "%0", e, "cx");

}



static __always_inline __must_check

bool refcount_add_not_zero(unsigned int i, refcount_t *r)

{

	int c, result;



	c = atomic_read(&(r->refs));

	do {

		if (unlikely(c == 0))

			return false;



		result = c + i;



		/* Did we try to increment from/to an undesirable state? */

		if (unlikely(c < 0 || c == INT_MAX || result < c)) {

			asm volatile(REFCOUNT_ERROR

				     : : [counter] "m" (r->refs.counter)

				     : "cc", "cx");

			break;

		}



	} while (!atomic_try_cmpxchg(&(r->refs), &c, result));



	return c != 0;

}



static __always_inline __must_check bool refcount_inc_not_zero(refcount_t *r)

{

	return refcount_add_not_zero(1, r);

}



#endif

include/linux/refcount.h

+4 −2
Original line number Diff line number Diff line
@@ -2,8 +2,10 @@ 
#define _LINUX_REFCOUNT_H



#include <linux/atomic.h>

#include <linux/mutex.h>

#include <linux/spinlock.h>

#include <linux/compiler.h>

#include <linux/spinlock_types.h>



struct mutex;



/**

 * refcount_t - variant of atomic_t specialized for reference counts

lib/refcount.c

+2 −0
Original line number Diff line number Diff line
@@ -34,7 +34,9 @@ 
 *

 */



#include <linux/mutex.h>

#include <linux/refcount.h>

#include <linux/spinlock.h>

#include <linux/bug.h>



#ifdef CONFIG_REFCOUNT_FULL