srcu: Remove needless rcu_seq_done() check while holding read lock
The srcu_gp_start_if_needed() function now read-holds the srcu_struct whose grace period is being started, which means that the corresponding SRCU grace period cannot end. This in turn means that the SRCU grace-period sequence number returned by rcu_seq_snap() cannot expire during this time. And that means that the calls to rcu_seq_done() in srcu_funnel_exp_start() and srcu_funnel_gp_start() can never return true. This commit therefore removes these rcu_seq_done() checks, but adds checks in kernels built with CONFIG_PROVE_RCU=y that splats if rcu_seq_done() does somehow return true. [ paulmck: Rearrange checks to handle kernels built with lockdep. ] Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> To: rcu@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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