rcu: Clean up after the SRCU-fastification of RCU Tasks Trace

Now that RCU Tasks Trace has been re-implemented in terms of SRCU-fast,
the ->trc_ipi_to_cpu, ->trc_blkd_cpu, ->trc_blkd_node, ->trc_holdout_list,
and ->trc_reader_special task_struct fields are no longer used.

In addition, the rcu_tasks_trace_qs(), rcu_tasks_trace_qs_blkd(),
exit_tasks_rcu_finish_trace(), and rcu_spawn_tasks_trace_kthread(),
show_rcu_tasks_trace_gp_kthread(), rcu_tasks_trace_get_gp_data(),
rcu_tasks_trace_torture_stats_print(), and get_rcu_tasks_trace_gp_kthread()
functions and all the other functions that they invoke are no longer used.

Also, the TRC_NEED_QS and TRC_NEED_QS_CHECKED CPP macros are no longer used.
Neither are the rcu_tasks_trace_lazy_ms and rcu_task_ipi_delay rcupdate
module parameters and the TASKS_TRACE_RCU_READ_MB Kconfig option.

This commit therefore removes all of them.

[ paulmck: Apply Alexei Starovoitov feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: bpf@vger.kernel.org
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

3 files changed, 1 insertions, 37 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index c5b30054cd01..bd5a420cf09a 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -175,36 +175,7 @@ void rcu_tasks_torture_stats_print(char *tt, char *tf);
 # define synchronize_rcu_tasks synchronize_rcu
 # endif
 
-# ifdef CONFIG_TASKS_TRACE_RCU
-// Bits for ->trc_reader_special.b.need_qs field.
-#define TRC_NEED_QS		0x1  // Task needs a quiescent state.
-#define TRC_NEED_QS_CHECKED	0x2  // Task has been checked for needing quiescent state.
-
-u8 rcu_trc_cmpxchg_need_qs(struct task_struct *t, u8 old, u8 new);
-void rcu_tasks_trace_qs_blkd(struct task_struct *t);
-
-# define rcu_tasks_trace_qs(t)							\
-	do {									\
-		int ___rttq_nesting = READ_ONCE((t)->trc_reader_nesting);	\
-										\
-		if (unlikely(READ_ONCE((t)->trc_reader_special.b.need_qs) == TRC_NEED_QS) &&	\
-		    likely(!___rttq_nesting)) {					\
-			rcu_trc_cmpxchg_need_qs((t), TRC_NEED_QS, TRC_NEED_QS_CHECKED);	\
-		} else if (___rttq_nesting && ___rttq_nesting != INT_MIN &&	\
-			   !READ_ONCE((t)->trc_reader_special.b.blocked)) {	\
-			rcu_tasks_trace_qs_blkd(t);				\
-		}								\
-	} while (0)
-void rcu_tasks_trace_torture_stats_print(char *tt, char *tf);
-# else
-# define rcu_tasks_trace_qs(t) do { } while (0)
-# endif
-
-#define rcu_tasks_qs(t, preempt)					\
-do {									\
-	rcu_tasks_classic_qs((t), (preempt));				\
-	rcu_tasks_trace_qs(t);						\
-} while (0)
+#define rcu_tasks_qs(t, preempt) rcu_tasks_classic_qs((t), (preempt))
 
 # ifdef CONFIG_TASKS_RUDE_RCU
 void synchronize_rcu_tasks_rude(void);
diff --git a/include/linux/rcupdate_trace.h b/include/linux/rcupdate_trace.h
index 3f46cbe67000..0bd47f12ecd1 100644
--- a/include/linux/rcupdate_trace.h
+++ b/include/linux/rcupdate_trace.h
@@ -136,9 +136,7 @@ static inline void rcu_barrier_tasks_trace(void)
 }
 
 // Placeholders to enable stepwise transition.
-void rcu_tasks_trace_get_gp_data(int *flags, unsigned long *gp_seq);
 void __init rcu_tasks_trace_suppress_unused(void);
-struct task_struct *get_rcu_tasks_trace_gp_kthread(void);
 
 #else
 /*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index fe39d422b37d..56156643ccac 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -946,11 +946,6 @@ struct task_struct {
 #ifdef CONFIG_TASKS_TRACE_RCU
 	int				trc_reader_nesting;
 	struct srcu_ctr __percpu	*trc_reader_scp;
-	int				trc_ipi_to_cpu;
-	union rcu_special		trc_reader_special;
-	struct list_head		trc_holdout_list;
-	struct list_head		trc_blkd_node;
-	int				trc_blkd_cpu;
 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 
 	struct sched_info		sched_info;