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Subject[PATCH tip/core/rcu 4/9] rcutorture: Emulate dyntick aspect of userspace nohz_full sojourn
Date
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
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