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locking: Introduce sync_core_before_usermode() 

Introduce an architecture function that ensures the current CPU
issues a core serializing instruction before returning to usermode.

This is needed for the membarrier "sync_core" command.

Architectures defining the sync_core_before_usermode() static inline
need to select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Andrew Hunter <ahh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Avi Kivity <avi@scylladb.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: David Sehr <sehr@google.com>
Cc: Greg Hackmann <ghackmann@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maged Michael <maged.michael@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-api@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/20180129202020.8515-7-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mathieu Desnoyers 2018-01-29 15:20:15 -05:00 committed by Ingo Molnar
parent 92485487ba
commit e61938a921
2 changed files with 24 additions and 0 deletions
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21
include/linux/sync_core.h Normal file
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@ -0,0 +1,21 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SYNC_CORE_H
#define _LINUX_SYNC_CORE_H
#ifdef CONFIG_ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
#include <asm/sync_core.h>
#else
/*
* This is a dummy sync_core_before_usermode() implementation that can be used
* on all architectures which return to user-space through core serializing
* instructions.
* If your architecture returns to user-space through non-core-serializing
* instructions, you need to write your own functions.
*/
static inline void sync_core_before_usermode(void)
{
}
#endif
#endif /* _LINUX_SYNC_CORE_H */

3
init/Kconfig
View File

@ -1918,3 +1918,6 @@ config ASN1
functions to call on what tags.
source "kernel/Kconfig.locks"
config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
bool