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Message-Id: <20200810072426.7180-2-dmtrmonakhov@yandex-team.ru>
Date: Mon, 10 Aug 2020 07:24:26 +0000
From: Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
To: linux-kernel@...r.kernel.org
Cc: koct9i@...il.com, Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
Subject: [PATCH 2/2] lib/test_lockup.c: allow cond_resched inside iteration
- New options:
cond_resched_inside=Y call cond_resched inside iteration under lock
measure_lockup=Y measure maximum lockup time
- Rename option:
call_cond_resched=Y -> cond_resched_outside=Y: call cond_resched()
between iterations.
This allow us to simulate situation where process call cond_resched()
with locks held.
Example demonstrate priority inversion issue with epbf-program, where
low priority task sheduled out while holding cgroup_mutex for a long
periods of time which blocks others high priority tasks.
CGROUP_MUTEX=$(gawk '$3 == "cgroup_mutex" {print "0x"$1}' /proc/kallsyms)
# Emulate ebpf-applications load which can hung inside cgroup_bpf_attach()
nice -20 modprobe lib/test_lockup.ko \
time_nsecs=1000 cooldown_nsecs=100000 iterations=100000 \
lock_mutex_ptr=$CGROUP_MUTEX reacquire_locks=Y\
cond_resched_inside=Y measure_lockup=Y &
stress-ng -c $(nproc) --timeout 10s&
time mkdir /sys/fs/cgroup/blkio/a
time rmdir /sys/fs/cgroup/blkio/a
Signed-off-by: Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
---
lib/test_lockup.c | 45 +++++++++++++++++++++++++++++++++++++--------
1 file changed, 37 insertions(+), 8 deletions(-)
diff --git a/lib/test_lockup.c b/lib/test_lockup.c
index 867b2f4..5666c00 100644
--- a/lib/test_lockup.c
+++ b/lib/test_lockup.c
@@ -73,9 +73,13 @@ static bool touch_hardlockup;
module_param(touch_hardlockup, bool, 0600);
MODULE_PARM_DESC(touch_hardlockup, "touch hard-lockup watchdog between iterations");
-static bool call_cond_resched;
-module_param(call_cond_resched, bool, 0600);
-MODULE_PARM_DESC(call_cond_resched, "call cond_resched() between iterations");
+static bool cond_resched_inside;
+module_param(cond_resched_inside, bool, 0600);
+MODULE_PARM_DESC(cond_resched_inside, "call cond_resched() during iteration");
+
+static bool cond_resched_outside;
+module_param(cond_resched_outside, bool, 0600);
+MODULE_PARM_DESC(cond_resched_outside, "call cond_resched() between iterations");
static bool measure_alloc_pages_wait;
module_param(measure_alloc_pages_wait, bool, 0400);
@@ -85,6 +89,10 @@ static bool measure_lock_wait;
module_param(measure_lock_wait, bool, 0400);
MODULE_PARM_DESC(measure_lock_wait, "measure lock wait time");
+static bool measure_lockup;
+module_param(measure_lockup, bool, 0400);
+MODULE_PARM_DESC(measure_lockup, "measure maximum lockup time");
+
static unsigned long lock_wait_threshold = ULONG_MAX;
module_param(lock_wait_threshold, ulong, 0400);
MODULE_PARM_DESC(lock_wait_threshold, "print lock wait time longer than this in nanoseconds, default off");
@@ -167,6 +175,7 @@ static atomic_t alloc_pages_failed = ATOMIC_INIT(0);
static atomic64_t max_lock_wait = ATOMIC64_INIT(0);
static atomic64_t max_alloc_pages_wait = ATOMIC64_INIT(0);
+static atomic64_t max_lockup_time = ATOMIC64_INIT(0);
static struct task_struct *main_task;
static int master_cpu;
@@ -369,6 +378,7 @@ static void test_wait(unsigned int secs, unsigned int nsecs)
static void test_lockup(bool master)
{
u64 lockup_start = local_clock();
+ u64 iter_start;
unsigned int iter = 0;
LIST_HEAD(pages);
@@ -379,12 +389,18 @@ static void test_lockup(bool master)
test_alloc_pages(&pages);
while (iter++ < iterations && !signal_pending(main_task)) {
+ s64 cur_lockup, max_lockup;
+
+ iter_start = local_clock();
if (iowait)
current->in_iowait = 1;
test_wait(time_secs, time_nsecs);
+ if (cond_resched_inside)
+ cond_resched();
+
if (iowait)
current->in_iowait = 0;
@@ -400,7 +416,15 @@ static void test_lockup(bool master)
if (touch_hardlockup)
touch_nmi_watchdog();
- if (call_cond_resched)
+ cur_lockup = local_clock() - iter_start;
+ max_lockup = atomic64_read(&max_lockup_time);
+ do {
+ if (cur_lockup < max_lockup)
+ break;
+ max_lockup = atomic64_cmpxchg(&max_lockup_time, max_lockup, cur_lockup);
+ } while (max_lockup != cur_lockup);
+
+ if (cond_resched_outside)
cond_resched();
test_wait(cooldown_secs, cooldown_nsecs);
@@ -515,8 +539,8 @@ static int __init test_lockup_init(void)
return -EINVAL;
#endif
- if ((wait_state != TASK_RUNNING ||
- (call_cond_resched && !reacquire_locks) ||
+ if ((wait_state != TASK_RUNNING || cond_resched_inside ||
+ (cond_resched_outside && !reacquire_locks) ||
(alloc_pages_nr && gfpflags_allow_blocking(alloc_pages_gfp))) &&
(test_disable_irq || disable_softirq || disable_preempt ||
lock_rcu || lock_spinlock_ptr || lock_rwlock_ptr)) {
@@ -552,7 +576,7 @@ static int __init test_lockup_init(void)
if (test_lock_sb_umount && test_inode)
lock_rwsem_ptr = (unsigned long)&test_inode->i_sb->s_umount;
- pr_notice("START pid=%d time=%u +%u ns cooldown=%u +%u ns iterations=%u state=%s %s%s%s%s%s%s%s%s%s%s%s\n",
+ pr_notice("START pid=%d time=%u +%u ns cooldown=%u +%u ns iterations=%u state=%s %s%s%s%s%s%s%s%s%s%s%s%s\n",
main_task->pid, time_secs, time_nsecs,
cooldown_secs, cooldown_nsecs, iterations, state,
all_cpus ? "all_cpus " : "",
@@ -564,7 +588,8 @@ static int __init test_lockup_init(void)
lock_read ? "lock_read " : "",
touch_softlockup ? "touch_softlockup " : "",
touch_hardlockup ? "touch_hardlockup " : "",
- call_cond_resched ? "call_cond_resched " : "",
+ cond_resched_inside ? "cond_resched_inside " : "",
+ cond_resched_outside ? "cond_resched_outside " : "",
reacquire_locks ? "reacquire_locks " : "");
if (alloc_pages_nr)
@@ -605,6 +630,10 @@ static int __init test_lockup_init(void)
pr_notice("Maximum pages allocation wait: %lld ns\n",
atomic64_read(&max_alloc_pages_wait));
}
+ if (measure_lockup)
+ pr_notice("Maximum lockup time: %lld ns\n",
+ atomic64_read(&max_lockup_time));
+
pr_notice("FINISH in %llu ns\n", local_clock() - test_start);
if (test_file)
--
2.7.4
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