On Wed, Jul 13, 2016 at 01:01:39PM -0700, Mark Johnston wrote: > On Wed, Jul 13, 2016 at 10:19:47PM +0300, Konstantin Belousov wrote: > > On Wed, Jul 13, 2016 at 09:42:47AM -0700, Mark Johnston wrote: > > > I'm having trouble determining if the diff changes any userland-visible > > > behaviour. It seems that the only potential problem with the current > > > p_xthread handling is in stopevent(), since a thread calling stopevent() > > > from postsig() may clear p_xthread after it was set by another thread in > > > ptracestop(). But I also don't understand why we call stopevent(S_SIG) > > > from both issignal() and postsig() - this would appear to stop the > > > thread twice for the same signal. > > You mean that the patch would not fix your issue ? Quite possible, it > > might require some more code to 'move the torch' to next xthread, so to > > say. When you write the test case, I will spend efforts on the working > > patch. > > I don't think this addresses my issue of the process remaining stopped > after the PT_DETACH, but see below. Patch tries to add some coordination to ptracestop(), I do not object to the statement that what was done is not enough.
> > > > > That said, I do not think that we should change anything about stopevent(), > > since this is code which is on life support. If we cannot remove procfs > > debugging interface, let not change it at least in incompatible ways. > > > > > > > > With respect to the desired direction, do you agree that the SIGSTOP > > > from PT_ATTACH should effectively be ignored if a different signal stops > > > the process first? As I said in a previous post, it seems that the > > > SA_STOP property of PT_ATTACH's SIGSTOP is not used in the common case, > > > since ptracestop() will stop the process if any signal is received, and > > > the PT_DETACH operation will typically overwrite the SIGSTOP with 0 in > > > td_xsig. > > Hmm, I think no, we can not make such change. Issue is, debugger > > interface guarantees (at least for single-threaded programs it is > > done correctly) that SIGSTOP is noted. In my opinion, it would be the > > incompatible API change. > > But this guarantee is not honoured in the single-threaded case where > PT_ATTACH sends SIGSTOP after another signal is already pending. This > other signal will stop the process in ptracestop(), so SIGSTOP will not > be reported until after a PT_CONTINUE or PT_DETACH, which seems to > violate the interface as you described it. Am I missing some reason > that this cannot occur? If not, I'll write a test case for the > single-threaded case first. Please give me some initial test case, I am fine with single-threaded case. I do not think that the mt test would be much different ? _______________________________________________ email@example.com mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"