Messages in this thread | | | Date | Thu, 3 Oct 2019 13:04:04 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: 4.19 dwarf unwinding broken |
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Em Thu, Oct 03, 2019 at 08:17:38AM -0700, Josh Hunt escreveu: > On 10/3/19 3:03 AM, Jiri Olsa wrote: > >On Thu, Oct 03, 2019 at 12:54:09AM -0700, Josh Hunt wrote: > >>The following commit is breaking dwarf unwinding on 4.19 kernels: > > > >how? > > When doing something like: > perf record -p $(cat /var/run/app.pid) -g --call-graph dwarf -F 999 > -- sleep 3 > > with 4.19.75 perf I see things like: > > app_Thr00 26247 1810131.375329: 168288 cycles:ppp: > > app_Thr01 26767 1810131.377449: 344415 cycles:ppp: > > uvm:WorkerThread 26746 1810131.383052: 504 cycles:ppp: > ffffffff9f77cce0 _raw_spin_lock+0x10 (/boot/vmlinux-4.19.46) > ffffffff9f181527 __perf_event_task_sched_in+0xf7 > (/boot/vmlinux-4.19.46) > ffffffff9f09a7b8 finish_task_switch+0x158 (/boot/vmlinux-4.19.46) > ffffffff9f778276 __schedule+0x2f6 (/boot/vmlinux-4.19.46) > ffffffff9f7787f2 schedule+0x32 (/boot/vmlinux-4.19.46) > ffffffff9f77bb0a schedule_hrtimeout_range_clock+0x8a > (/boot/vmlinux-4.19.46) > ffffffff9f22ea12 poll_schedule_timeout.constprop.6+0x42 > (/boot/vmlinux-4.19.46) > ffffffff9f22eeeb do_sys_poll+0x4ab (/boot/vmlinux-4.19.46) > ffffffff9f22fb7b __se_sys_poll+0x5b (/boot/vmlinux-4.19.46) > ffffffff9f0023de do_syscall_64+0x4e (/boot/vmlinux-4.19.46) > ffffffff9f800088 entry_SYSCALL_64+0x68 (/boot/vmlinux-4.19.46) > --- > > and with 4.19.75 perf with e5adfc3e7e77 reverted those empty call > stacks go away and also other call stacks show more thread details: > > uvm:WorkerThread 26746 1810207.336391: 1 cycles:ppp: > ffffffff9f181505 __perf_event_task_sched_in+0xd5 > (/boot/vmlinux-4.19.46) > ffffffff9f09a7b8 finish_task_switch+0x158 (/boot/vmlinux-4.19.46) > ffffffff9f778276 __schedule+0x2f6 (/boot/vmlinux-4.19.46) > ffffffff9f7787f2 schedule+0x32 (/boot/vmlinux-4.19.46) > ffffffff9f77bb0a schedule_hrtimeout_range_clock+0x8a > (/boot/vmlinux-4.19.46) > ffffffff9f22ea12 poll_schedule_timeout.constprop.6+0x42 > (/boot/vmlinux-4.19.46) > ffffffff9f22eeeb do_sys_poll+0x4ab (/boot/vmlinux-4.19.46) > ffffffff9f22fb7b __se_sys_poll+0x5b (/boot/vmlinux-4.19.46) > ffffffff9f0023de do_syscall_64+0x4e (/boot/vmlinux-4.19.46) > ffffffff9f800088 entry_SYSCALL_64+0x68 (/boot/vmlinux-4.19.46) > 7f7ef3f5c90d [unknown] (/lib/x86_64-linux-gnu/libc-2.23.so) > 3eb5c99 poll+0xc9 (inlined) > 3eb5c99 colib::ipc::EventFd::wait+0xc9 > (/usr/local/bin/app) > 3296779 uvm::WorkerThread::run+0x129 (/usr/local/bin/app) > ffffffffffffffff [unknown] ([unknown]) > > They also look the same as earlier kernel versions we have running. > > In addition reading e8ba2906f6b's changelog sounded very similar to > what I was seeing. This application launches a # of threads and is > definitely already running before the invocation of perf. > > Thanks for looking at this.
So, if at __event__synthesize_thread()
if (pid == tgid && perf_event__synthesize_mmap_events(tool, mmap_event, pid, tgid, process, machine, mmap_data))
We did something like:
if (pid != tgid && machine__find_thread(tgid, tgid) == NULL) { struct thread *t = thread__new(tgid, tgid);
then use the info for pid to get synthesize the thread group leader so that the get the sharing we need? }
- Arnaldo
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