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rcu-tasks: Repair RCU Tasks Trace quiescence check
[ Upstream commit 2eb52fa890
]
The context-switch-time check for RCU Tasks Trace quiescence expects
current->trc_reader_special.b.need_qs to be zero, and if so, updates
it to TRC_NEED_QS_CHECKED. This is backwards, because if this value
is zero, there is no RCU Tasks Trace grace period in flight, an thus
no need for a quiescent state. Instead, when a grace period starts,
this field is set to TRC_NEED_QS.
This commit therefore changes the check from zero to TRC_NEED_QS.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 2 additions and 2 deletions
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@ -189,9 +189,9 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
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do { \
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int ___rttq_nesting = READ_ONCE((t)->trc_reader_nesting); \
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\
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if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
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if (unlikely(READ_ONCE((t)->trc_reader_special.b.need_qs) == TRC_NEED_QS) && \
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likely(!___rttq_nesting)) { \
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rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
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rcu_trc_cmpxchg_need_qs((t), TRC_NEED_QS, TRC_NEED_QS_CHECKED); \
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} else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
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!READ_ONCE((t)->trc_reader_special.b.blocked)) { \
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rcu_tasks_trace_qs_blkd(t); \
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