On Tue, Mar 01, 2022 at 09:53:54AM -0500, Steven Rostedt wrote: > On Tue, 1 Mar 2022 10:05:12 +0100 > Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Mon, Feb 28, 2022 at 05:04:11PM -0800, Namhyung Kim wrote: > > > The __mutex_lock_slowpath() and friends are declared as noinline and > > > _RET_IP_ returns its caller as mutex_lock which is not meaningful. > > > Pass the ip from mutex_lock() to have actual caller info in the trace. > > > > Blergh, can't you do a very limited unwind when you do the tracing > > instead? 3 or 4 levels should be plenty fast and sufficient. > > Is there a fast and sufficient way that works across architectures? The normal stacktrace API? Or the fancy new arch_stack_walk() which is already available on most architectures you actually care about and risc-v :-) Remember, this is the contention path, we're going to stall anyway, doing a few levels of unwind shouldn't really hurt at that point. Anyway; when I wrote that this morning, I was thinking: unsigned long ips[4]; stack_trace_save(ips, 4, 0); > Could objtool help here? There's a contradition there... objtool is still x86_64 only :-/ IIRC there's been work on s390, arm64 and power objtool, but so far none of them actually made it in.
