On Sat, Oct 30, 2021 at 08:23:12PM +0800, Muchun Song wrote: > On Sat, Oct 30, 2021 at 6:12 PM Yunfeng Ye <yeyunfeng@xxxxxxxxxx> wrote: > > > > After the memory is freed, it may be allocated by other CPUs and has > > been recorded by trace. So the timing sequence of the memory tracing is > > inaccurate. > > > > For example, we expect the following timing sequeuce: > > > > CPU 0 CPU 1 > > > > (1) alloc xxxxxx > > (2) free xxxxxx > > (3) alloc xxxxxx > > (4) free xxxxxx > > > > However, the following timing sequence may occur: > > > > CPU 0 CPU 1 > > > > (1) alloc xxxxxx > > (2) alloc xxxxxx > > (3) free xxxxxx > > (4) free xxxxxx > > > > So place the trace before freeing memory in kmem_cache_free(). > > Could you tell me what problem you have encountered > here? It's confusing to see the memory allocated before it's freed. If you're unaware of this problem, you might think it was being used after free because (1) happened a long time ago, so you see (2) immediately followed by (3) and then see the memory being used. The patch makes sense to me.
