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Date: Wed, 29 Aug 2018 14:47:39 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 06/17] rcutorture: Add forward-progress tests for RCU grace periods
This commit adds a kthread that loops going into and out of RCU
read-side critical sections, but also including a cond_resched(),
optionally guarded by a check of need_resched(), in that same loop.
This commit relies solely on rcu_torture_writer() progress to judge
the forward progress of grace periods.
Note that Tasks RCU and SRCU are exempted from forward-progress testing
due their (intentionally) less-robust forward-progress guarantees.
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/rcutiny.h | 1 +
kernel/rcu/rcutorture.c | 73 ++++++++++++++++++++++++++++++++++++++++-
kernel/rcu/update.c | 1 +
3 files changed, 74 insertions(+), 1 deletion(-)
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 8d9a0ea8f0b5..a6353f3d6094 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -108,6 +108,7 @@ static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt)
*/
static inline void rcu_virt_note_context_switch(int cpu) { }
static inline void rcu_cpu_stall_reset(void) { }
+static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
static inline void rcu_idle_enter(void) { }
static inline void rcu_idle_exit(void) { }
static inline void rcu_irq_enter(void) { }
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 5df2411f7aee..fd3ce6cc8eea 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -89,6 +89,12 @@ torture_param(int, fqs_duration, 0,
"Duration of fqs bursts (us), 0 to disable");
torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
+torture_param(bool, fwd_progress, 1, "Test grace-period forward progress");
+torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
+torture_param(int, fwd_progress_holdoff, 60,
+ "Time between forward-progress tests (s)");
+torture_param(bool, fwd_progress_need_resched, 1,
+ "Hide cond_resched() behind need_resched()");
torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
torture_param(bool, gp_normal, false,
@@ -137,6 +143,7 @@ static struct task_struct **cbflood_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
static struct task_struct *stall_task;
+static struct task_struct *fwd_prog_task;
static struct task_struct **barrier_cbs_tasks;
static struct task_struct *barrier_task;
@@ -291,6 +298,7 @@ struct rcu_torture_ops {
void (*cb_barrier)(void);
void (*fqs)(void);
void (*stats)(void);
+ int (*stall_dur)(void);
int irq_capable;
int can_boost;
int extendables;
@@ -429,6 +437,7 @@ static struct rcu_torture_ops rcu_ops = {
.cb_barrier = rcu_barrier,
.fqs = rcu_force_quiescent_state,
.stats = NULL,
+ .stall_dur = rcu_jiffies_till_stall_check,
.irq_capable = 1,
.can_boost = rcu_can_boost(),
.name = "rcu"
@@ -1116,7 +1125,8 @@ rcu_torture_writer(void *arg)
break;
}
}
- rcu_torture_current_version++;
+ WRITE_ONCE(rcu_torture_current_version,
+ rcu_torture_current_version + 1);
/* Cycle through nesting levels of rcu_expedite_gp() calls. */
if (can_expedite &&
!(torture_random(&rand) & 0xff & (!!expediting - 1))) {
@@ -1660,6 +1670,63 @@ static int __init rcu_torture_stall_init(void)
return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
}
+/* Carry out grace-period forward-progress testing. */
+static int rcu_torture_fwd_prog(void *args)
+{
+ unsigned long cvar;
+ int idx;
+ unsigned long stopat;
+ bool tested = false;
+
+ VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
+ do {
+ schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
+ cvar = READ_ONCE(rcu_torture_current_version);
+ stopat = jiffies + cur_ops->stall_dur() / fwd_progress_div;
+ while (time_before(jiffies, stopat) && !torture_must_stop()) {
+ idx = cur_ops->readlock();
+ udelay(10);
+ cur_ops->readunlock(idx);
+ if (!fwd_progress_need_resched || need_resched())
+ cond_resched();
+ }
+ if (!time_before(jiffies, stopat) && !torture_must_stop()) {
+ tested = true;
+ WARN_ON_ONCE(cvar ==
+ READ_ONCE(rcu_torture_current_version));
+ }
+ /* Avoid slow periods, better to test when busy. */
+ stutter_wait("rcu_torture_fwd_prog");
+ } while (!torture_must_stop());
+ WARN_ON(!tested);
+ torture_kthread_stopping("rcu_torture_fwd_prog");
+ return 0;
+}
+
+/* If forward-progress checking is requested and feasible, spawn the thread. */
+static int __init rcu_torture_fwd_prog_init(void)
+{
+ if (!fwd_progress)
+ return 0; /* Not requested, so don't do it. */
+ if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0) {
+ VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
+ return 0;
+ }
+ if (stall_cpu > 0) {
+ VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
+ if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
+ return -EINVAL; /* In module, can fail back to user. */
+ WARN_ON(1); /* Make sure rcutorture notices conflict. */
+ return 0;
+ }
+ if (fwd_progress_holdoff <= 0)
+ fwd_progress_holdoff = 1;
+ if (fwd_progress_div <= 0)
+ fwd_progress_div = 4;
+ return torture_create_kthread(rcu_torture_fwd_prog,
+ NULL, fwd_prog_task);
+}
+
/* Callback function for RCU barrier testing. */
static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
{
@@ -1833,6 +1900,7 @@ rcu_torture_cleanup(void)
}
rcu_torture_barrier_cleanup();
+ torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
torture_stop_kthread(rcu_torture_stall, stall_task);
torture_stop_kthread(rcu_torture_writer, writer_task);
@@ -2104,6 +2172,9 @@ rcu_torture_init(void)
if (firsterr)
goto unwind;
firsterr = rcu_torture_stall_init();
+ if (firsterr)
+ goto unwind;
+ firsterr = rcu_torture_fwd_prog_init();
if (firsterr)
goto unwind;
firsterr = rcu_torture_barrier_init();
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 39cb23d22109..a6b860422d18 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -472,6 +472,7 @@ int rcu_jiffies_till_stall_check(void)
}
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
}
+EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
void rcu_sysrq_start(void)
{
--
2.17.1
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