Messages in this thread Patch in this message | | | From | Song Liu <> | Subject | Getting empty callchain from perf_callchain_kernel() | Date | Thu, 16 May 2019 23:51:55 +0000 |
| |
Hi,
We found a failure with selftests/bpf/tests_prog in test_stacktrace_map (on bpf/master branch).
After digging into the code, we found that perf_callchain_kernel() is giving empty callchain for tracepoint sched/sched_switch. And it seems related to commit
d15d356887e770c5f2dcf963b52c7cb510c9e42d ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")
Before this commit, perf_callchain_kernel() returns callchain with regs->ip. With this commit, regs->ip is not sent for !perf_hw_regs(regs) case.
I found the following change fixes the selftest. But I am not very sure, it is the best solution here.
Please share comments and suggestions on this.
Thanks in advance!
Song
diff --git i/arch/x86/events/core.c w/arch/x86/events/core.c index f315425d8468..7b8a9eb4d5fd 100644 --- i/arch/x86/events/core.c +++ w/arch/x86/events/core.c @@ -2402,9 +2402,9 @@ perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *re return; }
+ if (perf_callchain_store(entry, regs->ip)) + return; if (perf_hw_regs(regs)) { - if (perf_callchain_store(entry, regs->ip)) - return; unwind_start(&state, current, regs, NULL); } else { unwind_start(&state, current, NULL, (void *)regs->sp);
| |