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rcu-tasks: Remove second argument of rcu_read_unlock_trace_special()

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The second argument of rcu_read_unlock_trace_special() is always zero.
When called from exit_tasks_rcu_finish_trace(), it is the constant
zero, and rcu_read_unlock_trace_special() doesn't get called from
rcu_read_unlock_trace() unless the value of local variable "nesting"
is zero because in that case the early return is taken instead.

This commit therefore removes the "nesting" argument from the
rcu_read_unlock_trace_special() function, substituting the constant
zero within that function.  This commit also adds a WARN_ON_ONCE()
to rcu_read_lock_trace_held() in case non-zeroness some day appears.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2021-07-28 12:28:27 -07:00
parent 18f08e758f
commit a5c071ccfa
2 changed files with 6 additions and 5 deletions
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5
include/linux/rcupdate_trace.h
View File

@ -31,7 +31,7 @@ static inline int rcu_read_lock_trace_held(void)
#ifdef CONFIG_TASKS_TRACE_RCU
void rcu_read_unlock_trace_special(struct task_struct *t, int nesting);
void rcu_read_unlock_trace_special(struct task_struct *t);
/**
* rcu_read_lock_trace - mark beginning of RCU-trace read-side critical section
@ -80,7 +80,8 @@ static inline void rcu_read_unlock_trace(void)
WRITE_ONCE(t->trc_reader_nesting, nesting);
return; // We assume shallow reader nesting.
}
rcu_read_unlock_trace_special(t, nesting);
WARN_ON_ONCE(nesting != 0);
rcu_read_unlock_trace_special(t);
}
void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);

6
kernel/rcu/tasks.h
View File

@ -848,7 +848,7 @@ static void rcu_read_unlock_iw(struct irq_work *iwp)
static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
/* If we are the last reader, wake up the grace-period kthread. */
void rcu_read_unlock_trace_special(struct task_struct *t, int nesting)
void rcu_read_unlock_trace_special(struct task_struct *t)
{
int nq = READ_ONCE(t->trc_reader_special.b.need_qs);
@ -858,7 +858,7 @@ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting)
// Update .need_qs before ->trc_reader_nesting for irq/NMI handlers.
if (nq)
WRITE_ONCE(t->trc_reader_special.b.need_qs, false);
WRITE_ONCE(t->trc_reader_nesting, nesting);
WRITE_ONCE(t->trc_reader_nesting, 0);
if (nq && atomic_dec_and_test(&trc_n_readers_need_end))
irq_work_queue(&rcu_tasks_trace_iw);
}
@ -1200,7 +1200,7 @@ static void exit_tasks_rcu_finish_trace(struct task_struct *t)
WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting));
WRITE_ONCE(t->trc_reader_nesting, 0);
if (WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)))
rcu_read_unlock_trace_special(t, 0);
rcu_read_unlock_trace_special(t);
}
/**