From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 01/17] rcu: Avoid ->dynticks_nmi_nesting store tearing
Date: Fri, 1 Dec 2017 11:36:32 -0800 [thread overview]
Message-ID: <1512157008-22355-1-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171201193625.GA20681@linux.vnet.ibm.com>
NMIs can nest, and store tearing could in theory happen on carries
from one byte to the next. This commit therefore adds the WRITE_ONCE()
macros preventing this.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/tree.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index f9c0ca2ccf0c..c5d960f86cf8 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1103,7 +1103,8 @@ void rcu_nmi_enter(void)
rcu_dynticks_eqs_exit();
incby = 1;
}
- rdtp->dynticks_nmi_nesting += incby;
+ WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */
+ rdtp->dynticks_nmi_nesting + incby);
barrier();
}
@@ -1135,12 +1136,13 @@ void rcu_nmi_exit(void)
* leave it in non-RCU-idle state.
*/
if (rdtp->dynticks_nmi_nesting != 1) {
- rdtp->dynticks_nmi_nesting -= 2;
+ WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */
+ rdtp->dynticks_nmi_nesting - 2);
return;
}
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
- rdtp->dynticks_nmi_nesting = 0;
+ WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
rcu_dynticks_eqs_enter();
}
--
2.5.2
next prev parent reply other threads:[~2017-12-01 19:40 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-01 19:36 [PATCH tip/core/rcu 0/17] RCU dyntick updates for v4.16 Paul E. McKenney
2017-12-01 19:36 ` Paul E. McKenney [this message]
2017-12-01 19:36 ` [PATCH tip/core/rcu 02/17] rcu: Reduce dyntick-idle state space Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 03/17] rcu: Move rcu_nmi_{enter,exit}() to prepare for consolidation Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 04/17] rcu: Clamp ->dynticks_nmi_nesting at eqs entry/exit Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 05/17] rcu: Define rcu_irq_{enter,exit}() in terms of rcu_nmi_{enter,exit}() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 06/17] rcu: Make ->dynticks_nesting be a simple counter Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 07/17] rcu: Eliminate rcu_irq_enter_disabled() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 08/17] rcu: Add tracing to irq/NMI dyntick-idle transitions Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 09/17] rcu: Shrink ->dynticks_{nmi_,}nesting from long long to long Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 10/17] rcu: Add ->dynticks field to rcu_dyntick trace event Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 11/17] rcu: Stop duplicating lockdep checks in RCU's idle-entry code Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 12/17] rcu: Avoid ->dynticks_nesting store tearing Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 13/17] rcu: Fold rcu_eqs_enter_common() into rcu_eqs_enter() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 14/17] rcu: Fold rcu_eqs_exit_common() into rcu_eqs_exit() Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 15/17] rcu: Simplify rcu_eqs_{enter,exit}() non-idle task debug code Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 16/17] doc: Update dyntick-idle design documentation for NMI/irq consolidation Paul E. McKenney
2017-12-01 19:36 ` [PATCH tip/core/rcu 17/17] tracing, rcu: Remove no longer used trace event rcu_prep_idle Paul E. McKenney
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