Messages in this thread Patch in this message |  | | From | Dmitry Monakhov <> | Subject | [PATCH] lib/test_lockup.c: add parameters for cond_resched inside loop | Date | Sun, 9 Aug 2020 19:06:15 +0000 |
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call_cond_resched_before=Y call cond_resched with resource before wait call_cond_resched_after=Y call cond_resched with resource after wait measure_cond_resched=Y measure maximum cond_resched time inside loop
This simulate situation where process call cond_resched() with lock 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 programs with high priority.
CGROUP_MUTEX=$(gawk '$3 == "cgroup_mutex" {print "0x"$1}' /proc/kallsyms) # Emulate ebpf-application load which can hung inside cgroup_bpf_attach() nice -20 modprobe lib/test_lockup.ko \ time_nsecs=1000 cooldown_nsecs=100000 iterations=100000 \ lock_mutex_ptr=$CGROUP_MUTEX \ measure_lock_wait=Y call_cond_resched_after=Y &
stress-ng -c $(nproc) --timeout 10s& time mkdir /sys/fs/cgroup/blkio/a
Signed-off-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru> --- lib/test_lockup.c | 44 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 43 insertions(+), 1 deletion(-)
diff --git a/lib/test_lockup.c b/lib/test_lockup.c index 0f81252..3e05d6e 100644 --- a/lib/test_lockup.c +++ b/lib/test_lockup.c @@ -77,6 +77,18 @@ 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 call_cond_resched_before; +module_param(call_cond_resched_before, bool, 0600); +MODULE_PARM_DESC(call_cond_resched_before, "call cond_resched() before wait"); + +static bool call_cond_resched_after; +module_param(call_cond_resched_after, bool, 0600); +MODULE_PARM_DESC(call_cond_resched_after, "call cond_resched() after wait"); + +static bool measure_cond_resched; +module_param(measure_cond_resched, bool, 0400); +MODULE_PARM_DESC(measure_cond_resched, "measure cond_resched time"); + static bool measure_lock_wait; module_param(measure_lock_wait, bool, 0400); MODULE_PARM_DESC(measure_lock_wait, "measure lock wait time"); @@ -162,6 +174,7 @@ MODULE_PARM_DESC(lock_sb_umount, "lock file -> sb -> s_umount"); static atomic_t alloc_pages_failed = ATOMIC_INIT(0); static atomic64_t max_lock_wait = ATOMIC64_INIT(0); +static atomic64_t max_cond_resched = ATOMIC64_INIT(0); static struct task_struct *main_task; static int master_cpu; @@ -346,6 +359,22 @@ static void test_wait(unsigned int secs, unsigned int nsecs) } } +static void test_cond_resched(void) +{ + s64 cur, old_max; + s64 start = local_clock(); + + cond_resched(); + + cur = local_clock() - start; + old_max = atomic64_read(&max_cond_resched); + do { + if (cur < old_max) + break; + old_max = atomic64_cmpxchg(&max_cond_resched, old_max, cur); + } while (old_max != cur); +} + static void test_lockup(bool master) { u64 lockup_start = local_clock(); @@ -363,8 +392,14 @@ static void test_lockup(bool master) if (iowait) current->in_iowait = 1; + if (call_cond_resched_before) + test_cond_resched(); + test_wait(time_secs, time_nsecs); + if (call_cond_resched_after) + test_cond_resched(); + if (iowait) current->in_iowait = 0; @@ -497,6 +532,7 @@ static int __init test_lockup_init(void) if ((wait_state != TASK_RUNNING || (call_cond_resched && !reacquire_locks) || + call_cond_resched_before || call_cond_resched_after || (alloc_pages_nr && gfpflags_allow_blocking(alloc_pages_gfp))) && (test_disable_irq || disable_softirq || disable_preempt || lock_rcu || lock_spinlock_ptr || lock_rwlock_ptr)) { @@ -532,7 +568,7 @@ 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%s\n", main_task->pid, time_secs, time_nsecs, cooldown_secs, cooldown_nsecs, iterations, state, all_cpus ? "all_cpus " : "", @@ -545,6 +581,8 @@ static int __init test_lockup_init(void) touch_softlockup ? "touch_softlockup " : "", touch_hardlockup ? "touch_hardlockup " : "", call_cond_resched ? "call_cond_resched " : "", + call_cond_resched_before ? "call_cond_resched_before " : "", + call_cond_resched_after ? "call_cond_resched_after " : "", reacquire_locks ? "reacquire_locks " : ""); if (alloc_pages_nr) @@ -578,6 +616,10 @@ static int __init test_lockup_init(void) pr_notice("Maximum lock wait: %lld ns\n", atomic64_read(&max_lock_wait)); + if (measure_cond_resched) + pr_notice("Maximum cond resched time: %lld ns\n", + atomic64_read(&max_cond_resched)); + if (alloc_pages_nr) pr_notice("Page allocation failed %u times\n", atomic_read(&alloc_pages_failed)); -- 2.7.4
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