https://github.com/torvalds/linux
Revision 3a303258ef40a29dd4a3ebd29dcb16afd546bd59 authored by Linus Torvalds on 04 August 2016, 23:51:49 UTC, committed by Linus Torvalds on 04 August 2016, 23:51:49 UTC
Pull UBI/UBIFS updates from Richard Weinberger: "This contains mostly cleanups and minor improvements of UBI and UBIFS" * tag 'upstream-4.8-rc1' of git://git.infradead.org/linux-ubifs: ubi: Use bitmaps in Fastmap self-check code ubi: Be more paranoid while seaching for the most recent Fastmap ubi: Check whether the Fastmap anchor matches the super block ubi: Rework Fastmap attach base code ubi: Fix whitespace issue in count_fastmap_pebs() ubi: Introduce vol_ignored() ubi: Fix scan_fast() comment ubifs: switch_gc_head: Remove redondant sync of wbuf ubi: Make volume resize power cut aware ubi: Fix early logging ubi: gluebi: Fix double refcounting ubifs: Silence early error messages if MS_SILENT is set ubi: Fix race condition between ubi device creation and udev ubifs: Update comment for ubifs_errc ubi: Only read necessary size when reading the VID header ubifs: Make xattr structures static ubifs: Silence error output if MS_SILENT is set
Tip revision: 3a303258ef40a29dd4a3ebd29dcb16afd546bd59 authored by Linus Torvalds on 04 August 2016, 23:51:49 UTC
Merge tag 'upstream-4.8-rc1' of git://git.infradead.org/linux-ubifs
Merge tag 'upstream-4.8-rc1' of git://git.infradead.org/linux-ubifs
Tip revision: 3a30325
membarrier.c
/*
* Copyright (C) 2010, 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* membarrier system call
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/syscalls.h>
#include <linux/membarrier.h>
/*
* Bitmask made from a "or" of all commands within enum membarrier_cmd,
* except MEMBARRIER_CMD_QUERY.
*/
#define MEMBARRIER_CMD_BITMASK (MEMBARRIER_CMD_SHARED)
/**
* sys_membarrier - issue memory barriers on a set of threads
* @cmd: Takes command values defined in enum membarrier_cmd.
* @flags: Currently needs to be 0. For future extensions.
*
* If this system call is not implemented, -ENOSYS is returned. If the
* command specified does not exist, or if the command argument is invalid,
* this system call returns -EINVAL. For a given command, with flags argument
* set to 0, this system call is guaranteed to always return the same value
* until reboot.
*
* All memory accesses performed in program order from each targeted thread
* is guaranteed to be ordered with respect to sys_membarrier(). If we use
* the semantic "barrier()" to represent a compiler barrier forcing memory
* accesses to be performed in program order across the barrier, and
* smp_mb() to represent explicit memory barriers forcing full memory
* ordering across the barrier, we have the following ordering table for
* each pair of barrier(), sys_membarrier() and smp_mb():
*
* The pair ordering is detailed as (O: ordered, X: not ordered):
*
* barrier() smp_mb() sys_membarrier()
* barrier() X X O
* smp_mb() X O O
* sys_membarrier() O O O
*/
SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
{
if (unlikely(flags))
return -EINVAL;
switch (cmd) {
case MEMBARRIER_CMD_QUERY:
return MEMBARRIER_CMD_BITMASK;
case MEMBARRIER_CMD_SHARED:
if (num_online_cpus() > 1)
synchronize_sched();
return 0;
default:
return -EINVAL;
}
}
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