[PATCH] unwind: initialize unwind context only if given tcb is initialized

[Dmitry V. Levin]

On Fri, Apr 20, 2018 at 04:38:15AM +0300, Dmitry V. Levin wrote:
> On Fri, Apr 20, 2018 at 09:47:44AM +0900, Masatake YAMATO wrote:
> > On Fri, 20 Apr 2018 01:44:51 +0300, "Dmitry V. Levin" <ldv at altlinux.org> wrote:
> > >> --- a/strace.c
> > >> +++ b/strace.c
> > >> @@ -1783,6 +1783,8 @@ init(int argc, char *argv[])
> > >>  
> > >>  		unwind_init();
> > >>  		for (tcbi = 0; tcbi < tcbtabsize; ++tcbi) {
> > >> +			if (!tcbtab[tcbi]->pid)
> > >> +				continue;
> > >>  			unwind_tcb_init(tcbtab[tcbi]);
> > >>  		}
> > >>  	}
> > > 
> > > Apparently, we don't need this loop at all, there is no use to call
> > > unwind_tcb_init until the tracee is actually attached.  The proper place
> > > for unwind_tcb_init invocation is the same as for newoutf.
> > > I've pushed a few commits to implement this change.
> > 
> > Much better fix.
> > The function name is also improved.
> > 
> > One thing I cannot be convince is the following code block:
> > 
> >     static struct tcb *
> >     maybe_switch_tcbs(struct tcb *tcp, const int pid)
> >     {
> > 	    ...	
> > 	    tcp->pid = pid;
> > 
> > pid of tcb is updated. I wonder whether unwind context can be attached
> > well to the modified(?) tcb.
> 
> Good catch, looks like this code is out of date as more fields were added
> to struct tcb.  I suppose switching whole structures might be a better
> alternative to cherry-picking relevant fields.

On second thought, maybe_switch_tcbs already swaps whole structures
except a few pid-related fields.  So the question is, do we have
any more pid-related fields that should be excluded?


-- 
ldv
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