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rcutorture: Emulate dyntick aspect of userspace nohz_full sojourn 

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@kernel.org>
This commit is contained in:
Paul E. McKenney 2019-08-04 13:17:35 -07:00
parent 96926686de
commit 79ba7ff5a9
3 changed files with 13 additions and 0 deletions
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1
include/linux/rcutiny.h
View File

@ -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(); }

11
kernel/rcu/rcutorture.c
View File

@ -1761,6 +1761,11 @@ 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;
}
@ -1835,6 +1840,7 @@ 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;
@ -1894,6 +1900,11 @@ 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);

1
kernel/rcu/tree.c
View File

@ -375,6 +375,7 @@ void 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