Hi Max,
On Mon, Sep 30, 2013 at 06:49:22AM +0400, Max Filippov wrote:
> On Mon, Sep 30, 2013 at 6:29 AM, Baruch Siach <[email protected]> wrote:
> > On Mon, Sep 30, 2013 at 04:23:47AM +0400, Max Filippov wrote:
> >> On Sun, Sep 29, 2013 at 3:58 PM, Baruch Siach <[email protected]> wrote:
> >> > According to create_thread(3): "The new thread does not inherit the
> >> > creating
> >> > thread's alternate signal stack". Since commit f9a3879a (Fix sigaltstack
> >> > corruption among cloned threads), current->sas_ss_size is set to 0 for
> >> > cloned
> >> > processes sharing VM with their parent. Don't use the (nonexistent)
> >> > alternate
> >> > signal stack in this case.
> >> >
> >> > Fixes the SA_ONSTACK part of the nptl/tst-cancel20 test from uClibc.
> >> >
> >> > Also fix a checkpatch.pl error, while at it.
> >> >
> >> > Cc: <[email protected]>
> >> > Signed-off-by: Baruch Siach <[email protected]>
> >> > ---
> >> > arch/xtensa/kernel/signal.c | 3 ++-
> >> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/arch/xtensa/kernel/signal.c b/arch/xtensa/kernel/signal.c
> >> > index 718eca1..ef94d82 100644
> >> > --- a/arch/xtensa/kernel/signal.c
> >> > +++ b/arch/xtensa/kernel/signal.c
> >> > @@ -341,7 +341,8 @@ static int setup_frame(int sig, struct k_sigaction
> >> > *ka, siginfo_t *info,
> >> >
> >> > sp = regs->areg[1];
> >> >
> >> > - if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
> >> > + if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && !on_sig_stack(sp)
> >> > + && current->sas_ss_size != 0) {
> >>
> >> Looks like
> >> if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
> >> is used more often here among other arches. Mind changing it this way?
> >
> > According to the commit log of 0f8f30892 (x86: signal: check sas_ss_size
> > instead of sas_ss_flags()) "Checking on_sig_stack() in sas_ss_flags() at
> > get_sigframe() is redundant and not correct on 64 bit". The 64 bit part
> > doesn't apply here, but I guess the redundant part does. Isn't it?
>
> The redundancy mentioned in that commit is due to the outer "if
> (!onsigstack)";
> in our case "!on_sig_stack(sp)" is explicitly checked in the same expression,
> and I'm proposing to get rid of it.
OK then. I'll update and resend.
baruch
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