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rcu: Add WRITE_ONCE() to rcu_state ->gp_start

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The rcu_state structure's ->gp_start field is read locklessly, so this
commit adds the WRITE_ONCE() to an update in order to provide proper
documentation and READ_ONCE()/WRITE_ONCE() pairing.

This data race was reported by KCSAN.  Not appropriate for backporting
due to failure being unlikely.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2020-01-20 15:29:04 -08:00
parent 57721fd15a
commit 59881bcd85
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tree_stall.h
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@ -102,7 +102,7 @@ static void record_gp_stall_check_time(void)
unsigned long j = jiffies;
unsigned long j1;
rcu_state.gp_start = j;
WRITE_ONCE(rcu_state.gp_start, j);
j1 = rcu_jiffies_till_stall_check();
/* Record ->gp_start before ->jiffies_stall. */
smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */