On Mon, Jan 16, 2012 at 08:15:38PM +0530, Srikar Dronamraju wrote: > > > > I've tested following event: > > echo "p:probe_libc/free /lib64/libc-2.13.so:0x7a4f0 %ax" > ./uprobe_events > > > > and commands like: > > perf record -a -e probe_libc:free --filter "common_pid == 1127" > > perf record -e probe_libc:free --filter "arg1 == 0xa" ls > > > > got me proper results. > > > > Okay thanks for the inputs. > > > thanks, > > jirka > > > > --- > > The preemption needs to be disabled when submitting data into perf. > > I actually looked at other places where perf_trace_buf_prepare and > perf_trace_buf_submit are being called. for example perf_syscall_enter > and perf_syscall_exit both call the above routines and they didnt seem > to be called with premption disabled. Is that the way perf probe is > called in our case that needs us to call pre-emption here? Did you see a > case where calling these without preemption disabled caused a problem? the perf_trace_buf_prepare touches per cpu variables, hence the preemption disabling the perf_trace_buf_prepare code is used by syscalls, kprobes, and trace events - both syscalls and trace events are implemented by tracepoints which disable preemption before calling the probe (see __DO_TRACE macro in include/linux/tracepoint.h) - kprobes disable preemption as well (kprobe_handler in arch/x86/kernel/kprobes.c) haven't checked the optimalized kprobes, but should be the same case jirka > > > > --- > > kernel/trace/trace_uprobe.c | 6 +++++- > > 1 files changed, 5 insertions(+), 1 deletions(-) > > > > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c > > index af29368..4d3857c 100644 > > --- a/kernel/trace/trace_uprobe.c > > +++ b/kernel/trace/trace_uprobe.c > > @@ -653,9 +653,11 @@ static void uprobe_perf_func(struct trace_uprobe *tp, struct pt_regs *regs) > > "profile buffer not large enough")) > > return; > > > > + preempt_disable(); > > + > > entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx); > > if (!entry) > > - return; > > + goto out; > > > > entry->ip = get_uprobe_bkpt_addr(task_pt_regs(current)); > > data = (u8 *)&entry[1]; > > @@ -665,6 +667,8 @@ static void uprobe_perf_func(struct trace_uprobe *tp, struct pt_regs *regs) > > > > head = this_cpu_ptr(call->perf_events); > > perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head); > > + out: > > + preempt_enable(); > > } > > #endif /* CONFIG_PERF_EVENTS */ > > > > -- > Thanks and Regards > Srikar > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>