On Thu, 2020-03-26 at 11:28 +1100, Michael Ellerman wrote:
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> Joakim Tjernlund <joakim.tjernl...@infinera.com> writes:
> > On Mon, 2020-03-23 at 15:45 +0100, Christophe Leroy wrote:
> > > Le 23/03/2020 à 15:43, Christophe Leroy a écrit :
> > > > Le 23/03/2020 à 15:17, Joakim Tjernlund a écrit :
> > > > > In __die(), see below, there is this call to notify_send() with
> > > > > SIGSEGV hardcoded, this seems odd
> > > > > to me as the variable "err" holds the true signal(in my case SIGBUS)
> > > > > Should not SIGSEGV be replaced with the true signal no.?
> > > >
> > > > As far as I can see, comes from
> > > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fid%3D66fcb1059&data=02%7C01%7CJoakim.Tjernlund%40infinera.com%7Caa316058f9e34dd758c808d7d11ca391%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C0%7C637207793252449714&sdata=LBzRMxHWJzNEztnnG0UzJb7PHvaDGVswQD%2B8WpY9YX8%3D&reserved=0
> > > >
> > >
> > > And
> > > https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fid%3Dae87221d3ce49d9de1e43756da834fd0bf05a2ad&data=02%7C01%7CJoakim.Tjernlund%40infinera.com%7Caa316058f9e34dd758c808d7d11ca391%7C285643de5f5b4b03a1530ae2dc8aaf77%7C1%7C0%7C637207793252449714&sdata=Dh%2BUTRgG85oVSgC3SCR1B7izQH4HofT4ppOMiy9xvDA%3D&reserved=0
> > > shows it is (was?) similar on x86.
> > >
> >
> > I tried to follow that chain thinking it would end up sending a signal to
> > user space but I cannot see
> > that happens. Seems to be related to debugging.
> >
> > In short, I cannot see any signal being delivered to user space. If so that
> > would explain why
> > our user space process never dies.
> > Is there a signal hidden in machine_check handler for SIGBUS I cannot see?
>
> It's platform specific. What platform are you on?
I am on e500, e5500(e500mc) and 83xx :)
>
> See the ppc_md & cur_cpu_spec calls here:
>
> void machine_check_exception(struct pt_regs *regs)
> {
> int recover = 0;
> bool nested = in_nmi();
> if (!nested)
> nmi_enter();
>
> __this_cpu_inc(irq_stat.mce_exceptions);
>
> add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
>
> /* See if any machine dependent calls. In theory, we would want
> * to call the CPU first, and call the ppc_md. one if the CPU
> * one returns a positive number. However there is existing code
> * that assumes the board gets a first chance, so let's keep it
> * that way for now and fix things later. --BenH.
> */
> if (ppc_md.machine_check_exception)
> recover = ppc_md.machine_check_exception(regs);
> else if (cur_cpu_spec->machine_check)
> recover = cur_cpu_spec->machine_check(regs);
>
> if (recover > 0)
> goto bail;
>
>
> Either the ppc_md or cpu_spec handlers can send a signal, but after a
> bit of grepping I think only the pseries and powernv ones do.
Seems so
>
> If you get into die() then it's an oops, which is not the same as a
> normal signal.
Exactly, and the die/OOPS does not seem work as intended either. The system
tries to limp along
and generates more similar OOPses and may even hang.
>
> cheers
