[M3devel] chosing SIG_SUSPEND?

[Tony Hosking]

Yes, we want a signal no-one else is using to stop the threads.

On 21 Jan 2009, at 08:37, Jay wrote:

>
> Solaris at least currently has SIGRTMAX.
> I want to switch RTSignalC.c to "something" here.
> I can preserve compat, like
>
> #ifdef __sun
> SIGUSR2
> #else..
>
> or..?
>
> I could do
> #ifdef SIGUSR2
> #define SIG_SUSPEND SIGUSR2
> #elif defined(SIGRTMAX)
> #define SIG_SUSPEND SIGRTMAX
> #else
> #error
> #endif
>
> I'll go with a compatible version for now and you can change it if  
> you want.
> I'll test on Linux/x86, FreeBSD (AMD64, but hopefully there is gcc - 
> m32),
> Linux/PPC, Solaris, Cygwin, Darwin/PPC (uh, actually, no, Darwin isn't
> really relevant, but I'll make sure the result does what is intended.)
>
> It looks like SIGRTMAX is a function call on Solaris.
>
> This stuff is like broken, right?
> I mean, there's a small number of signals and there's no arbitration.
> People just take them over and hope nobody else cares.
>
>
> There's no way to just queue a function call to a thread, in  
> portable/general?
> Windows has QueueUserAPC or SuspendThread (SuspendThread is dangerous,
> thread could be doing anything), QueueUserAPC only interrupts at  
> certain times.
>
>
> - Jay
>
>
> ----------------------------------------
>> From: hosking at cs.purdue.edu
>> To: jay.krell at cornell.edu
>> Date: Wed, 21 Jan 2009 03:42:01 +1100
>> CC: m3devel at elegosoft.com
>> Subject: Re: [M3devel] chosing SIG_SUSPEND?
>>
>> Choose SIGRTMAX first if defined, then SIGUSR2. I don't thing NSIG-1
>> is reliable, but just works on some systems.
>>
>> On 21 Jan 2009, at 01:12, Jay wrote:
>>
>>>
>>> What is the algorithm for chosing SIG_SUSPEND?
>>>
>>> Something like:
>>>
>>> #include
>>>
>>> #ifdef __APPLE__
>>> /* nothing -- SIG_SUSPEND not used */
>>> #elif defined(NSIG)
>>> #define SIG_SUSPEND (NSIG - 1)
>>> #elif defined(_NSIG)
>>> #define SIG_SUSPEND (_NSIG - 1)
>>> #elif defined(SIGRTMAX)
>>> #define SIG_SUSPEND SIGRTMAX
>>> #else
>>> #define SIG_SUSPEND SIGUSR2
>>> #endif
>>>
>>> ?
>>>
>>> Whatever it is, I think it should be in RTSignalC.c.
>>>
>>> - Jay
>>