Indeed. We did some work with RS485 support for the Serial plugin... EINTRs 
happen all the time... recommended to retry (see Linux documentation around 
the web as to why). Obviously, in a plugin, the retry can happen quite 
quickly. Not sure how using FFI might respond.

Regards, Gary.

----- Original Message ----- 
From: "David T. Lewis" <lewis at mail.msen.com>
To: "The general-purpose Squeak developers list" 
<squeak-dev at lists.squeakfoundation.org>
Sent: Monday, January 26, 2009 1:50 AM
Subject: Re: [squeak-dev] Help needed with select() socket function and 
signalhandlers in squeakVM


> On Sun, Jan 25, 2009 at 08:50:35PM -0200, Mariano Martinez Peck wrote:
>>
>> Now, I have a problem with select() invocation. This function returns -1.
>> And the printf of the errno (where select() stores the errors), says: 
>> "Error
>> with select function: Interrupted system call" which means I am getting a
>> EINTR error. If you see console, you can see something like this:
>>
>> timeval tv_usec value: 0
>> timeval tv_sec value: 3
>> timeval tv_usec value: 0
>> timeval tv_sec value: 2
>> timeval tv_usec value: 996000
>> timeval tv_sec value: 3
>> timeval tv_usec value: 0
>> Error with select function: Interrupted system call
>>
>>
>> I asked Norbert (openDBX author) and he tell me exactly this:
>>
>> "An interrupted system call is something very normal because signals can 
>> be
>> sent
>> at every time to the application, either by the system or by the user. I
>> guess, in the Squeak code there is some signal handler installed, which 
>> does
>> something if one of the defined signals arrive.
>>
>> What I will do is to hide the consequences (returning an error) by 
>> looking
>> at
>> the error value and reenter the select call if the system call is
>> interrupted."
>
> Norbert is correct, and his solution of reentering the system call sounds
> like the right thing to do.
>
>> All I know is squeakVM is written it SLANG and then that's transformed to 
>> C.
>> So, squeakVM runs in C. So, there is where it can be a signal handler ? 
>> Is
>> there some way to change that from squeak (image) ?
>
> Any interrupt handler will service interrupts for the entire VM, so this 
> is
> not something that you would want to set up for a specific plugin. If one
> plugin sets a signal handler, it affects all other plugins as well as the
> VM itself.
>
> It is actually quite easy to experiment with setting signal handlers if
> you are using a Unix VM and if you have OSProcess installed. For example,
> if you want to handle the SIGQUIT signal, you can evualate the expression
> 'OSProcess accessor forwardSigQuit' to get a Smalltalk semaphore that will 
> be
> signalled each time the operating system sends a SIGQUIT (signal number 3)
> to the VM. You can have a Squeak process that waits on the semaphore and 
> does
> whatever you like.
>
> To be clear however, Norbert's explanation is correct regardless of how
> the VM chooses to handle a signal. When a system call such as select is
> interrupted, the application (your plugin) needs to check for this and
> retry the system call.
>
> HTH,
>
> Dave
>
>