Re: signal dequeue ...

[george anzinger <george@mvista.com>]

Davide Libenzi wrote:
> 
> On 22-Jun-2001 george anzinger wrote:
> > Davide Libenzi wrote:
> >>
> >> I'm just trying to figure out the reason why signal must be delivered one at
> >> a
> >> time instead of building a frame with multiple calls with only the last one
> >> chaining back to the kernel.
> >> All previous calls instead of calling the stub that jump back to the kernel
> >> will call a small stub like ( Ix86 ) :
> >>
> >> stkclean_stub:
> >>         add $frame_size, %esp
> >>         cmp %esp, $end_stubs
> >>         jae $sigreturn_stub
> >>         ret
> >> sigreturn_stub:
> >>         mov __NR_sigreturn, %eax
> >>         int $0x80
> >> end_stubs:
> >>
> >> ...
> >> | context1
> >> * $stkclean_stub
> >> * sigh1_eip
> >> | context0
> >> * $stkclean_stub
> >> * sigh0_eip
> >>
> >> When sigh0 return, it'll call stkclean_stub that will clean context0 and if
> >> we're at the end it'll call the jump-back-to-kernel stub, otherwise the
> >> it'll
> >> execute the  ret  the will call sigh1 handler ... and so on.
> >>
> > And if the user handler does a long_jmp?
> 
> But if the user handler does a long_jump even the old stub will be missed,
> isn't it ?

Right, but the remaining signals are still pending.  In your method, the
kernel doesn't know which were and which were not actually delivered.

George