lkml.org 
[lkml]   [2022]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3/3] kfence: test: try to avoid test_gfpzero trigger rcu_stall
From
Date
On 3/8/22 6:47 PM, Peng Liu wrote:
> When CONFIG_KFENCE_DYNAMIC_OBJECTS is set to a big number, kfence
> kunit-test-case test_gfpzero will eat up nearly all the CPU's
> resources and rcu_stall is reported as the following log which is
> cut from a physical server.
>
> rcu: INFO: rcu_sched self-detected stall on CPU
> rcu: 68-....: (14422 ticks this GP) idle=6ce/1/0x4000000000000002
> softirq=592/592 fqs=7500 (t=15004 jiffies g=10677 q=20019)
> Task dump for CPU 68:
> task:kunit_try_catch state:R running task
> stack: 0 pid: 9728 ppid: 2 flags:0x0000020a
> Call trace:
> dump_backtrace+0x0/0x1e4
> show_stack+0x20/0x2c
> sched_show_task+0x148/0x170
> ...
> rcu_sched_clock_irq+0x70/0x180
> update_process_times+0x68/0xb0
> tick_sched_handle+0x38/0x74
> ...
> gic_handle_irq+0x78/0x2c0
> el1_irq+0xb8/0x140
> kfree+0xd8/0x53c
> test_alloc+0x264/0x310 [kfence_test]
> test_gfpzero+0xf4/0x840 [kfence_test]
> kunit_try_run_case+0x48/0x20c
> kunit_generic_run_threadfn_adapter+0x28/0x34
> kthread+0x108/0x13c
> ret_from_fork+0x10/0x18
>
> To avoid rcu_stall and unacceptable latency, a schedule point is
> added to test_gfpzero.
>
> Signed-off-by: Peng Liu <liupeng256@huawei.com>
> ---
> mm/kfence/kfence_test.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
> index caed6b4eba94..1b50f70a4c0f 100644
> --- a/mm/kfence/kfence_test.c
> +++ b/mm/kfence/kfence_test.c
> @@ -627,6 +627,7 @@ static void test_gfpzero(struct kunit *test)
> kunit_warn(test, "giving up ... cannot get same object back\n");
> return;
> }
> + cond_resched();

This sounds like a band-aid - is there a better way to fix this?

> }
>
> for (i = 0; i < size; i++)
>

thanks,
-- Shuah

\
 
 \ /
  Last update: 2022-03-09 22:42    [W:0.102 / U:1.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site