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Message-Id: <1519682192-31987-2-git-send-email-paulmck@linux.vnet.ibm.com>
Date: Mon, 26 Feb 2018 13:56:29 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
fweisbec@...il.com, oleg@...hat.com,
Ildar Ismagilov <devix84@...il.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/5] srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap
From: Ildar Ismagilov <devix84@...il.com>
SRCU checks each srcu_data structure's grace-period number for counter
wrap four times per cycle by default. This frequency guarantees that
normal comparisons will detect potential wrap. However, the expedited
grace-period number is not checked. The consquences are not too horrible
(a failure to expedite a grace period when requested), but it would be
good to avoid such things. This commit therefore adds this check to
the expedited grace-period number.
Signed-off-by: Ildar Ismagilov <devix84@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
kernel/rcu/srcutree.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 01f4a8bf0e03..bb9607baad9b 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -579,6 +579,9 @@ static void srcu_gp_end(struct srcu_struct *sp)
if (ULONG_CMP_GE(gpseq,
sdp->srcu_gp_seq_needed + 100))
sdp->srcu_gp_seq_needed = gpseq;
+ if (ULONG_CMP_GE(gpseq,
+ sdp->srcu_gp_seq_needed_exp + 100))
+ sdp->srcu_gp_seq_needed_exp = gpseq;
spin_unlock_irqrestore_rcu_node(sdp, flags);
}
}
--
2.5.2
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