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rcu-tasks: Make RCU Tasks Trace make use of RCU scheduler hooks

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This commit makes the calls to rcu_tasks_qs() detect and report
quiescent states for RCU tasks trace.  If the task is in a quiescent
state and if ->trc_reader_checked is not yet set, the task sets its own
->trc_reader_checked.  This will cause the grace-period kthread to
remove it from the holdout list if it still remains there.

[ paulmck: Fix conditional compilation per kbuild test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney
2020-03-16 20:38:29 -07:00
parent af051ca4e4
commit 43766c3ead
4 changed files with 43 additions and 14 deletions
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5
kernel/rcu/tasks.h
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@@ -180,7 +180,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
/* Pick up any new callbacks. */
raw_spin_lock_irqsave(&rtp->cbs_lock, flags);
smp_mb__after_unlock_lock(); // Order updates vs. GP.
smp_mb__after_spinlock(); // Order updates vs. GP.
list = rtp->cbs_head;
rtp->cbs_head = NULL;
rtp->cbs_tail = &rtp->cbs_head;
@@ -874,7 +874,7 @@ static void rcu_tasks_trace_pertask(struct task_struct *t,
struct list_head *hop)
{
WRITE_ONCE(t->trc_reader_need_end, false);
t->trc_reader_checked = false;
WRITE_ONCE(t->trc_reader_checked, false);
t->trc_ipi_to_cpu = -1;
trc_wait_for_one_reader(t, hop);
}
@@ -983,6 +983,7 @@ static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp)
pr_err("\t%d holdouts\n", atomic_read(&trc_n_readers_need_end));
}
smp_mb(); // Caller's code must be ordered after wakeup.
// Pairs with pretty much every ordering primitive.
}
/* Report any needed quiescent state for this exiting task. */

6
kernel/rcu/tree_plugin.h
View File

@@ -331,8 +331,7 @@ void rcu_note_context_switch(bool preempt)
rcu_qs();
if (rdp->exp_deferred_qs)
rcu_report_exp_rdp(rdp);
if (!preempt)
rcu_tasks_qs(current);
rcu_tasks_qs(current, preempt);
trace_rcu_utilization(TPS("End context switch"));
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
@@ -841,8 +840,7 @@ void rcu_note_context_switch(bool preempt)
this_cpu_write(rcu_data.rcu_urgent_qs, false);
if (unlikely(raw_cpu_read(rcu_data.rcu_need_heavy_qs)))
rcu_momentary_dyntick_idle();
if (!preempt)
rcu_tasks_qs(current);
rcu_tasks_qs(current, preempt);
out:
trace_rcu_utilization(TPS("End context switch"));
}