From: Rik van Riel <riel@surriel.com>
To: linux-kernel@vger.kernel.org
Cc: kernel-team@fb.com, mingo@kernel.org, peterz@infradead.org,
luto@kernel.org, x86@kernel.org, efault@gmx.de,
dave.hansen@intel.com, Rik van Riel <riel@surriel.com>
Subject: [PATCH 01/11] x86,tlb: clarify memory barrier in switch_mm_irqs_off
Date: Wed, 1 Aug 2018 06:02:45 -0400 [thread overview]
Message-ID: <20180801100255.4278-2-riel@surriel.com> (raw)
In-Reply-To: <20180801100255.4278-1-riel@surriel.com>
Clarify exactly what the memory barrier synchronizes with.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rik van Riel <riel@surriel.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/mm/tlb.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 752dbf4e0e50..5321e02c4e09 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -263,8 +263,11 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
/*
* Read the tlb_gen to check whether a flush is needed.
* If the TLB is up to date, just use it.
- * The barrier synchronizes with the tlb_gen increment in
- * the TLB shootdown code.
+ * The TLB shootdown code first increments tlb_gen, and then
+ * sends IPIs to CPUs that have this CPU loaded and are not
+ * in lazy TLB mode. The barrier ensures we handle
+ * cpu_tlbstate.is_lazy before tlb_gen, keeping this code
+ * synchronized with the TLB flush code.
*/
smp_mb();
next_tlb_gen = atomic64_read(&next->context.tlb_gen);
--
2.14.4
next prev parent reply other threads:[~2018-08-01 10:03 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-01 10:02 [PATCH v2 0/11] x86,tlb,mm: more lazy TLB cleanups & optimizations Rik van Riel
2018-08-01 10:02 ` Rik van Riel [this message]
2018-08-01 10:02 ` [PATCH 02/11] smp: use __cpumask_set_cpu in on_each_cpu_cond Rik van Riel
2018-08-01 10:02 ` [PATCH 03/11] smp,cpumask: introduce on_each_cpu_cond_mask Rik van Riel
2018-08-01 10:02 ` [PATCH 04/11] x86,mm: use on_each_cpu_cond for TLB flushes Rik van Riel
2018-08-01 10:02 ` [PATCH 05/11] mm,tlb: turn dummy defines into inline functions Rik van Riel
2018-08-01 10:02 ` [PATCH 06/11] mm,x86: skip cr4 and ldt reload when mm stays the same Rik van Riel
2018-08-01 10:02 ` [PATCH 07/11] x86,mm: remove leave_mm cpu argument Rik van Riel
2018-08-01 10:02 ` [PATCH 08/11] arch,mm: add config variable to skip lazy TLB mm refcounting Rik van Riel
2018-08-01 10:02 ` [PATCH 09/11] mm,x86: shoot down lazy TLB references at exit_mmap time Rik van Riel
2018-08-01 10:02 ` [PATCH 10/11] x86,tlb: really leave mm on shootdown Rik van Riel
2018-08-01 10:02 ` [PATCH 11/11] mm,sched: conditionally skip lazy TLB mm refcounting Rik van Riel
2018-08-03 15:56 ` Peter Zijlstra
2018-08-03 16:40 ` Rik van Riel
2018-08-03 17:25 ` Peter Zijlstra
2018-08-03 17:39 ` Rik van Riel
2018-08-06 17:50 ` Peter Zijlstra
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