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author | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-04-14 18:30:22 -0700 |
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committer | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-05-28 09:06:09 -0700 |
commit | ab21f6081f7bc09a0918ef888de795d59a907c1a (patch) | |
tree | c6a0838e28969de0a8b9a14cecc455634a9e5678 | |
parent | 52b23be7ee023d7f1b67e7a20443ef352c7b5d2d (diff) | |
download | linux-ab21f6081f7bc09a0918ef888de795d59a907c1a.tar.bz2 |
rcutorture: Give the scheduler a chance on PREEMPT && NO_HZ_FULL kernels
In !PREEMPT kernels, cond_resched() is a no-op. In NO_HZ_FULL kernels,
in-kernel execution (such as that of rcutorture's kthreads) might extend
indefinitely without the scheduler gaining the aid of a scheduling-clock
interrupt. This combination can make the interaction of an rcutorture
forward-progress test and a CPU-hotplug stop_machine operation make less
forward progress than one might like. Additionally, Sebastian Siewior
notes that NO_HZ_FULL kernels have a scheduler check upon return to
userspace execution, which suggests that in-kernel emulation of tight
userspace loops containing system calls doing call_rcu() might also need
explicit checks in the PREEMPT && NO_HZ_FULL case.
This commit therefore introduces a rcu_torture_fwd_prog_cond_resched()
function that explicitly invokes schedule() in such kernels whenever
need_resched() returns true, while retaining use of cond_resched()
for kernels that are either !PREEMPT or !NO_HZ_FULL.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
-rw-r--r-- | kernel/rcu/rcutorture.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 6a4558532eac..ef6f6dedf4c4 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1667,6 +1667,17 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) spin_unlock_irqrestore(&rcu_fwd_lock, flags); } +// Give the scheduler a chance, even on nohz_full CPUs. +static void rcu_torture_fwd_prog_cond_resched(void) +{ + if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) { + if (need_resched()) + schedule(); + } else { + cond_resched(); + } +} + /* * Free all callbacks on the rcu_fwd_cb_head list, either because the * test is over or because we hit an OOM event. @@ -1690,7 +1701,7 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void) spin_unlock_irqrestore(&rcu_fwd_lock, flags); kfree(rfcp); freed++; - cond_resched(); + rcu_torture_fwd_prog_cond_resched(); } return freed; } @@ -1734,7 +1745,7 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) udelay(10); cur_ops->readunlock(idx); if (!fwd_progress_need_resched || need_resched()) - cond_resched(); + rcu_torture_fwd_prog_cond_resched(); } (*tested_tries)++; if (!time_before(jiffies, stopat) && @@ -1817,7 +1828,7 @@ static void rcu_torture_fwd_prog_cr(void) rfcp->rfc_gps = 0; } cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr); - cond_resched(); + rcu_torture_fwd_prog_cond_resched(); } stoppedat = jiffies; n_launders_cb_snap = READ_ONCE(n_launders_cb); |