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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2018-01-29 15:20:13 -0500
committerIngo Molnar <mingo@kernel.org>2018-02-05 21:34:31 +0100
commitc5f58bd58f432be5d92df33c5458e0bcbee3aadf (patch)
tree0a7c6d59b6101cd22de8a7da86b75010c84c199f /include/linux/sched
parent306e060435d7a3aef8f6f033e43b0f581638adce (diff)
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.h6
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