Hi Oleg, On Tue, 10 Dec 2013 16:57:44 +0100, Oleg Nesterov wrote: > On 12/10, Masami Hiramatsu wrote: >> >> (2013/12/09 15:20), Namhyung Kim wrote: >> > From: Oleg Nesterov <o...@redhat.com> >> > >> > uprobe_trace_print() and uprobe_perf_print() need to pass the additional >> > info to call_fetch() methods, currently there is no simple way to do this. >> > >> > current->utask looks like a natural place to hold this info, but we need >> > to allocate it before handler_chain(). >> > >> > This is a bit unfortunate, perhaps we will find a better solution later, >> > but this is simnple and should work right now. >> >> Hmm, when this will happen? > > Perhaps never. Perhaps it will stay forever and we remove get_utask() from > pre_ssout() (it is not needed after this patch). > > However I still think we can cleanup this. And to remind, we need to clean > the usage of utask->vaddr in trace_uprobe.c anyway. We can either try to > find another place to pass the info, or we can create a helper(s) for the > tracing handlers to access (and populate if NULL) utask->handler_data. > Note that this (probably) also makes sense because we can unexport > "struct uprobe_task" (but this needs a couple of off-topic cleanups). > > We will see. Lets do the minimal change which can work right now, Namhyung > has enough more serious problems ;)
Very true. :) > >> and isn't it better to increment >> miss-hit counter of the uprobe? > > What do you mean? This is not miss-hit and ->utask == NULL is quite normal. > For example, on ppc it can be always NULL because ppc likely emulates the > probed insn. Yes, for x86, it's always NULL at first but then populated after doing single-step. What we try to do is just moving the allocation before calling handler since we need to carry some information through it. Thanks, Namhyung > > Or did you mean that if get_utask() fails we should report this somehow? > Well, GFP_KERNEL should "never" fail and even if it fails we will restart > the same insn and retry the allocation. > > Or did I miss your point completely ? > > Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
