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rcutorture: Emulate userspace sojourn during call_rcu() floods

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During an actual call_rcu() flood, there would be frequent trips to
userspace (in-kernel call_rcu() floods must be otherwise housebroken).
Userspace execution allows a great many things to interrupt execution,
and rcutorture needs to also allow such interruptions.  This commit
therefore causes call_rcu() floods to occasionally invoke schedule(),
thus preventing spurious rcutorture failures due to other parts of the
kernel becoming irate at the call_rcu() flood events.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney 2019-06-22 14:35:59 -07:00
parent f4e8352928
commit bd1bfc51a3
1 changed files with 7 additions and 5 deletions
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12
kernel/rcu/rcutorture.c
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@ -1713,12 +1713,14 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
} }
// Give the scheduler a chance, even on nohz_full CPUs. // Give the scheduler a chance, even on nohz_full CPUs.
static void rcu_torture_fwd_prog_cond_resched(void) static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
{ {
if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) { if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
if (need_resched()) // Real call_rcu() floods hit userspace, so emulate that.
if (need_resched() || (iter & 0xfff))
schedule(); schedule();
} else { } else {
// No userspace emulation: CB invocation throttles call_rcu()
cond_resched(); cond_resched();
} }
} }
@ -1746,7 +1748,7 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void)
spin_unlock_irqrestore(&rcu_fwd_lock, flags); spin_unlock_irqrestore(&rcu_fwd_lock, flags);
kfree(rfcp); kfree(rfcp);
freed++; freed++;
rcu_torture_fwd_prog_cond_resched(); rcu_torture_fwd_prog_cond_resched(freed);
} }
return freed; return freed;
} }
@ -1790,7 +1792,7 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
udelay(10); udelay(10);
cur_ops->readunlock(idx); cur_ops->readunlock(idx);
if (!fwd_progress_need_resched || need_resched()) if (!fwd_progress_need_resched || need_resched())
rcu_torture_fwd_prog_cond_resched(); rcu_torture_fwd_prog_cond_resched(1);
} }
(*tested_tries)++; (*tested_tries)++;
if (!time_before(jiffies, stopat) && if (!time_before(jiffies, stopat) &&
@ -1875,7 +1877,7 @@ static void rcu_torture_fwd_prog_cr(void)
rfcp->rfc_gps = 0; rfcp->rfc_gps = 0;
} }
cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr); cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
rcu_torture_fwd_prog_cond_resched(); rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
} }
stoppedat = jiffies; stoppedat = jiffies;
n_launders_cb_snap = READ_ONCE(n_launders_cb); n_launders_cb_snap = READ_ONCE(n_launders_cb);