Ping: [PATCH v2 1/2] linux-user: Map low priority rt signals

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Tue, 2024-02-13 at 07:51 +0100, Philippe Mathieu-Daudé wrote:
> Cc'ing Brian & Taylor
> 
> On 12/2/24 21:45, Ilya Leoshkevich wrote:
> > Some applications want to use low priority realtime signals (e.g.,
> > SIGRTMAX). Currently QEMU cannot map all target realtime signals to
> > host signals, and chooses to sacrifice the end of the target
> > realtime
> > signal range.
> > 
> > Change this to the middle of that range, hoping that fewer
> > applications
> > will need it.
> > 
> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> > ---
> >   linux-user/signal.c | 18 +++++++++++++-----
> >   1 file changed, 13 insertions(+), 5 deletions(-)
> > 
> > diff --git a/linux-user/signal.c b/linux-user/signal.c
> > index d3e62ab030f..a81533b563a 100644
> > --- a/linux-user/signal.c
> > +++ b/linux-user/signal.c
> > @@ -511,13 +511,14 @@ static int core_dump_signal(int sig)
> >   
> >   static void signal_table_init(void)
> >   {
> > -    int hsig, tsig, count;
> > +    int hsig, hsig_count, tsig, tsig_count, tsig_hole,
> > tsig_hole_size, count;
> >   
> >       /*
> > -     * Signals are supported starting from TARGET_SIGRTMIN and
> > going up
> > -     * until we run out of host realtime signals.  Glibc uses the
> > lower 2
> > -     * RT signals and (hopefully) nobody uses the upper ones.
> > -     * This is why SIGRTMIN (34) is generally greater than
> > __SIGRTMIN (32).
> > +     * Signals are supported starting from TARGET_SIGRTMIN and up
> > to
> > +     * TARGET_SIGRTMAX, potentially with a hole in the middle of
> > this
> > +     * range, which, hopefully, nobody uses. Glibc uses the lower
> > 2 RT
> > +     * signals; this is why SIGRTMIN (34) is generally greater
> > than
> > +     * __SIGRTMIN (32).
> >        * To fix this properly we would need to do manual signal
> > delivery
> >        * multiplexed over a single host signal.
> >        * Attempts for configure "missing" signals via sigaction
> > will be
> > @@ -536,9 +537,16 @@ static void signal_table_init(void)
> >       host_to_target_signal_table[SIGABRT] = 0;
> >       host_to_target_signal_table[hsig++] = TARGET_SIGABRT;
> >   
> > +    hsig_count = SIGRTMAX - hsig + 1;
> > +    tsig_count = TARGET_NSIG - TARGET_SIGRTMIN + 1;
> > +    tsig_hole_size = tsig_count - MIN(hsig_count, tsig_count);
> > +    tsig_hole = TARGET_SIGRTMIN + (tsig_count - tsig_hole_size) /
> > 2;
> >       for (tsig = TARGET_SIGRTMIN;
> >            hsig <= SIGRTMAX && tsig <= TARGET_NSIG;
> >            hsig++, tsig++) {
> > +        if (tsig == tsig_hole) {
> > +            tsig += tsig_hole_size;
> > +        }
> >           host_to_target_signal_table[hsig] = tsig;
> >       }
> >   

Ping.

I wonder if it would make sense to make this configurable?