On Tue, Aug 30, 2022 at 10:37:17AM +0800, Hou Tao wrote: > Hi, > > On 8/30/2022 9:13 AM, Martin KaFai Lau wrote: > > On Mon, Aug 29, 2022 at 10:27:52PM +0800, Hou Tao wrote: > >> From: Hou Tao <houtao1@xxxxxxxxxx> > >> > >> When there are concurrent task local storage lookup operations, > >> if updates on per-cpu bpf_task_storage_busy is not preemption-safe, > >> some updates will be lost due to interleave, the final value of > >> bpf_task_storage_busy will not be zero and bpf_task_storage_trylock() > >> on specific cpu will fail forever. > >> > >> So add a test case to ensure the update of per-cpu bpf_task_storage_busy > >> is preemption-safe. > > This test took my setup 1.5 minute to run > > and cannot reproduce after running the test in a loop. > > > > Can it be reproduced in a much shorter time ? > > If not, test_maps is probably a better place to do the test. > I think the answer is No. I have think about adding the test in test_maps, but > the test case needs running a bpf program to check whether the value of > bpf_task_storage_busy is OK, so for simplicity I add it in test_progs. > If the running time is the problem, I can move it into test_maps. > > I assume it can be reproduced in arm with this test? Or it can > > also be reproduced in other platforms with different kconfig. > > Please paste the test failure message and the platform/kconfig > > to reproduce it in the commit message. > On arm64 it can be reproduced probabilistically when CONFIG_PREEMPT is enabled > on 2-cpus VM as show below. You can try to increase the value of nr and loop if > it still can not be reproduced. I don't have arm64 environment now, so cannot try it out. Please move the test to test_maps. If it is CONFIG_PREEMPT only, you can also check if CONFIG_PREEMPT is set or not and skip the test. Take a look at __kconfig usage under bpf/progs.
