On Mon, Jun 14, 2021 at 10:25 PM Pavel Skripkin <paskripkin@xxxxxxxxx> wrote: > > On Mon, 14 Jun 2021 22:19:10 +0800 > Dongliang Mu <mudongliangabcd@xxxxxxxxx> wrote: > > > On Mon, Jun 14, 2021 at 9:34 PM Pavel Skripkin <paskripkin@xxxxxxxxx> > > wrote: > > > > > > On Mon, 14 Jun 2021 21:22:43 +0800 > > > Dongliang Mu <mudongliangabcd@xxxxxxxxx> wrote: > > > > > > > Dear kernel developers, > > > > > > > > I was trying to debug the crash - memory leak in hwsim_add_one [1] > > > > recently. However, I encountered a disgusting issue: my > > > > breakpoint and printk/pr_alert in the functions that will be > > > > surely executed do not work. The stack trace is in the following. > > > > I wrote this email to ask for some suggestions on how to debug > > > > such cases? > > > > > > > > Thanks very much. Looking forward to your reply. > > > > > > > > > > Hi, Dongliang! > > > > > > This bug is not similar to others on the dashboard. I spent some > > > time debugging it a week ago. The main problem here, that memory > > > allocation happens in the boot time: > > > > > > > [<ffffffff84359255>] kernel_init+0xc/0x1a7 init/main.c:1447 > > > > > > > Oh, nice catch. No wonder why my debugging does not work. :( > > > > > and reproducer simply tries to > > > free this data. You can use ftrace to look at it. Smth like this: > > > > > > $ echo 'hwsim_*' > $TRACE_DIR/set_ftrace_filter > > > > Thanks for your suggestion. > > > > Do you have any conclusions about this case? If you have found out the > > root cause and start writing patches, I will turn my focus to other > > cases. > > No, I had some busy days and I have nothing about this bug for now. > I've just traced the reproducer execution and that's all :) > > I guess, some error handling paths are broken, but Im not sure In the beginning, I agreed with you. However, after I manually checked functions: hwsim_probe (initialization) and hwsim_remove (cleanup), then things may be different. The cleanup looks correct to me. I would like to debug but stuck with the debugging process. And there is another issue: the cleanup function also does not output anything or hit the breakpoint. I don't quite understand it since the cleanup is not at the boot time. Any idea? > > > > > > BTW, I only found another possible memory leak after some manual code > > review [1]. However, it is not the root cause for this crash. > > > > [1] https://lkml.org/lkml/2021/6/10/1297 > > > > > > > > would work. > > > > > > > > > With regards, > > > Pavel Skripkin > > > > > With regards, > Pavel Skripkin
