Messages in this thread |  | | Date | Tue, 10 Dec 2013 16:57:44 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 16/17] uprobes: Allocate ->utask before handler_chain() for tracing handlers |
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On 12/10, Masami Hiramatsu wrote: > > (2013/12/09 15:20), Namhyung Kim wrote: > > From: Oleg Nesterov <oleg@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 ;)
> 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.
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.
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