From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
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, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 09/12] srcu: Apply *_ONCE() to ->srcu_last_gp_end
Date: Mon, 9 Dec 2019 20:07:38 -0800 [thread overview]
Message-ID: <20191210040741.2943-9-paulmck@kernel.org> (raw)
In-Reply-To: <20191210040714.GA2715@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@kernel.org>
The ->srcu_last_gp_end field is accessed from any CPU at any time
by synchronize_srcu(), so non-initialization references need to use
READ_ONCE() and WRITE_ONCE(). This commit therefore makes that change.
Reported-by: syzbot+08f3e9d26e5541e1ecf2@syzkaller.appspotmail.com
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/srcutree.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 5dffade..21acdff 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -530,7 +530,7 @@ static void srcu_gp_end(struct srcu_struct *ssp)
idx = rcu_seq_state(ssp->srcu_gp_seq);
WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);
cbdelay = srcu_get_delay(ssp);
- ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
+ WRITE_ONCE(ssp->srcu_last_gp_end, ktime_get_mono_fast_ns());
rcu_seq_end(&ssp->srcu_gp_seq);
gpseq = rcu_seq_current(&ssp->srcu_gp_seq);
if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq))
@@ -762,6 +762,7 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp)
unsigned long flags;
struct srcu_data *sdp;
unsigned long t;
+ unsigned long tlast;
/* If the local srcu_data structure has callbacks, not idle. */
local_irq_save(flags);
@@ -780,9 +781,9 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp)
/* First, see if enough time has passed since the last GP. */
t = ktime_get_mono_fast_ns();
+ tlast = READ_ONCE(ssp->srcu_last_gp_end);
if (exp_holdoff == 0 ||
- time_in_range_open(t, ssp->srcu_last_gp_end,
- ssp->srcu_last_gp_end + exp_holdoff))
+ time_in_range_open(t, tlast, tlast + exp_holdoff))
return false; /* Too soon after last GP. */
/* Next, check for probable idleness. */
--
2.9.5
next prev parent reply other threads:[~2019-12-10 4:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-10 4:07 [PATCH tip/core/rcu 0/12] Miscellaneous fixes for v5.6 Paul E. McKenney
2019-12-10 4:07 ` [PATCH tip/core/rcu 01/12] rcu: Remove rcu_swap_protected() paulmck
2019-12-11 3:35 ` Martin K. Petersen
2019-12-11 3:51 ` Paul E. McKenney
2019-12-11 18:37 ` Paul E. McKenney
2019-12-11 19:09 ` Matthias Brugger
2019-12-11 23:12 ` Paul E. McKenney
2019-12-12 9:31 ` Kalle Valo
[not found] ` <87mubxdh52.fsf@kamboji.qca.qualcomm.com>
2019-12-12 18:21 ` Paul E. McKenney
2019-12-10 4:07 ` [PATCH tip/core/rcu 02/12] rcu: Mark non-global functions and variables as static paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 03/12] rcu: Fix harmless omission of "CONFIG_" from #if condition paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 04/12] rcu: Fix tracepoint tracking RCU CPU kthread utilization paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 05/12] rcu: Remove the declaration of call_rcu() in tree.h paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 06/12] rcu: Move gp_state_names[] and gp_state_getname() to tree_stall.h paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 07/12] rcu: Move rcu_{expedited,normal} definitions into rcupdate.h paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 08/12] rcu: Switch force_qs_rnp() to for_each_leaf_node_cpu_mask() paulmck
2019-12-10 4:07 ` paulmck [this message]
2019-12-10 4:07 ` [PATCH tip/core/rcu 10/12] .mailmap: Add entries for old paulmck@kernel.org addresses paulmck
2019-12-11 19:03 ` Florian Fainelli
2019-12-11 23:14 ` Paul E. McKenney
2019-12-10 4:07 ` [PATCH tip/core/rcu 11/12] powerpc: Remove comment about read_barrier_depends() paulmck
2019-12-10 4:07 ` [PATCH tip/core/rcu 12/12] rcu: Remove unused stop-machine #include paulmck
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