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| author |   Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | 2018-01-29 15:20:13 -0500 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2018-02-05 21:34:31 +0100 |
| commit | c5f58bd58f432be5d92df33c5458e0bcbee3aadf (patch) | |
| tree | 0a7c6d59b6101cd22de8a7da86b75010c84c199f /include/linux/sched | |
| parent | membarrier: Document scheduler barrier requirements (diff) | |
| download | linux-dev-c5f58bd58f432be5d92df33c5458e0bcbee3aadf.tar.xz linux-dev-c5f58bd58f432be5d92df33c5458e0bcbee3aadf.zip | |
membarrier: Provide GLOBAL_EXPEDITED command
Allow expedited membarrier to be used for data shared between processes
through shared memory.
Processes wishing to receive the membarriers register with
MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED. Those which want to issue
membarrier invoke MEMBARRIER_CMD_GLOBAL_EXPEDITED.
This allows extremely simple kernel-level implementation: we have almost
everything we need with the PRIVATE_EXPEDITED barrier code. All we need
to do is to add a flag in the mm_struct that will be used to check
whether we need to send the IPI to the current thread of each CPU.
There is a slight downside to this approach compared to targeting
specific shared memory users: when performing a membarrier operation,
all registered "global" receivers will get the barrier, even if they
don't share a memory mapping with the sender issuing
MEMBARRIER_CMD_GLOBAL_EXPEDITED.
This registration approach seems to fit the requirement of not
disturbing processes that really deeply care about real-time: they
simply should not register with MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED.
In order to align the membarrier command names, the "MEMBARRIER_CMD_SHARED"
command is renamed to "MEMBARRIER_CMD_GLOBAL", keeping an alias of
MEMBARRIER_CMD_SHARED to MEMBARRIER_CMD_GLOBAL for UAPI header backward
compatibility.
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: 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
Link: http://lkml.kernel.org/r/20180129202020.8515-5-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/sched')
| -rw-r--r-- | include/linux/sched/mm.h | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index b84e0fde1d72..1c4e40c5efaf 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -219,8 +219,10 @@ static inline void memalloc_noreclaim_restore(unsigned int flags) #ifdef CONFIG_MEMBARRIER enum { - MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0), - MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1), + MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0), + MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1), + MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2), + MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3), }; #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS |