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From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	jiangshanlai@gmail.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	"Paul E. McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH tip/core/rcu 4/9] rcutorture: Emulate dyntick aspect of userspace nohz_full sojourn
Date: Wed,  2 Oct 2019 18:47:23 -0700
Message-ID: <20191003014728.13496-4-paulmck@kernel.org> (raw)
In-Reply-To: <20191003014710.GA13323@paulmck-ThinkPad-P72>

From: "Paul E. McKenney" <paulmck@linux.ibm.com>

During an actual call_rcu() flood, there would be frequent trips to
userspace (in-kernel call_rcu() floods must be otherwise housebroken).
Userspace execution on nohz_full CPUs implies an RCU dyntick idle/not-idle
transition pair, so this commit adds emulation of that pair.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
 include/linux/rcutiny.h |  1 +
 kernel/rcu/rcutorture.c | 11 +++++++++++
 kernel/rcu/tree.c       |  1 +
 3 files changed, 13 insertions(+)

diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 9bf1dfe..37b6f0c 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -84,6 +84,7 @@ static inline void rcu_scheduler_starting(void) { }
 #endif /* #else #ifndef CONFIG_SRCU */
 static inline void rcu_end_inkernel_boot(void) { }
 static inline bool rcu_is_watching(void) { return true; }
+static inline void rcu_momentary_dyntick_idle(void) { }
 
 /* Avoid RCU read-side critical sections leaking across. */
 static inline void rcu_all_qs(void) { barrier(); }
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 3c9feca..7dcb2b8 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1759,6 +1759,11 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void)
 		kfree(rfcp);
 		freed++;
 		rcu_torture_fwd_prog_cond_resched(freed);
+		if (tick_nohz_full_enabled()) {
+			local_irq_save(flags);
+			rcu_momentary_dyntick_idle();
+			local_irq_restore(flags);
+		}
 	}
 	return freed;
 }
@@ -1833,6 +1838,7 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
 static void rcu_torture_fwd_prog_cr(void)
 {
 	unsigned long cver;
+	unsigned long flags;
 	unsigned long gps;
 	int i;
 	long n_launders;
@@ -1891,6 +1897,11 @@ static void rcu_torture_fwd_prog_cr(void)
 		}
 		cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
 		rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
+		if (tick_nohz_full_enabled()) {
+			local_irq_save(flags);
+			rcu_momentary_dyntick_idle();
+			local_irq_restore(flags);
+		}
 	}
 	stoppedat = jiffies;
 	n_launders_cb_snap = READ_ONCE(n_launders_cb);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8110514..5692db5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -375,6 +375,7 @@ static void __maybe_unused rcu_momentary_dyntick_idle(void)
 	WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR));
 	rcu_preempt_deferred_qs(current);
 }
+EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
 
 /**
  * rcu_is_cpu_rrupt_from_idle - see if interrupted from idle
-- 
2.9.5


  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-03  1:47 [PATCH tip/core/rcu 0/9] Torture-test updates Paul E. McKenney
2019-10-03  1:47 ` [PATCH tip/core/rcu 1/9] rcu: Remove unused function rcutorture_record_progress() paulmck
2019-10-03  1:47 ` [PATCH tip/core/rcu 2/9] locktorture: Replace strncmp() with str_has_prefix() paulmck
2019-10-03  1:47 ` [PATCH tip/core/rcu 3/9] rcutorture: Remove CONFIG_HOTPLUG_CPU=n from scenarios paulmck
2019-10-03  1:47 ` paulmck [this message]
2019-10-03  1:47 ` [PATCH tip/core/rcu 5/9] rcu: Remove unused variable rcu_perf_writer_state paulmck
2019-10-03  1:47 ` [PATCH tip/core/rcu 6/9] rcutorture: Separate warnings for each failure type paulmck
2019-10-03  1:47 ` [PATCH tip/core/rcu 7/9] rcutorture: Make in-kernel-loop testing more brutal paulmck
2019-10-03  1:47 ` [PATCH tip/core/rcu 8/9] locking: locktorture: Do not include rwlock.h directly paulmck
2019-10-03  1:47 ` [PATCH tip/core/rcu 9/9] rcu: Suppress levelspread uninitialized messages paulmck
2019-10-03  8:53   ` Geert Uytterhoeven
2019-10-05 16:16     ` Paul E. McKenney

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