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rcu: Mark writes to rcu_sync ->gp_count field
The rcu_sync structure's ->gp_count field is updated under the protection of ->rss_lock, but read locklessly, and KCSAN noted the data race. This commit therefore uses WRITE_ONCE() to do this update to clearly document its racy nature. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
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@ -122,7 +122,7 @@ void rcu_sync_enter(struct rcu_sync *rsp)
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* we are called at early boot time but this shouldn't happen.
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*/
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}
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rsp->gp_count++;
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WRITE_ONCE(rsp->gp_count, rsp->gp_count + 1);
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spin_unlock_irq(&rsp->rss_lock);
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if (gp_state == GP_IDLE) {
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@ -151,11 +151,15 @@ void rcu_sync_enter(struct rcu_sync *rsp)
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*/
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void rcu_sync_exit(struct rcu_sync *rsp)
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{
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int gpc;
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WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_IDLE);
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WARN_ON_ONCE(READ_ONCE(rsp->gp_count) == 0);
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spin_lock_irq(&rsp->rss_lock);
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if (!--rsp->gp_count) {
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gpc = rsp->gp_count - 1;
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WRITE_ONCE(rsp->gp_count, gpc);
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if (!gpc) {
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if (rsp->gp_state == GP_PASSED) {
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WRITE_ONCE(rsp->gp_state, GP_EXIT);
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rcu_sync_call(rsp);
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