From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Graf <p.graf@itknet.de>
To: ecos-discuss@sources.redhat.com
Subject: Re: [ECOS] sscanf() vs. fgetc()
Date: Thu, 12 Jul 2001 03:45:00 -0000
Message-id: <3.0.5.32.20010712123601.0090f2e0@128.128.128.220>
References: <3.0.5.32.20010712104805.00914420@128.128.128.220> <86sng24g1c.fsf@halftrack.hq.acn-group.ch>
X-SW-Source: 2001-07/msg00347.html

Hi Robin,

>> But when I use sscanf() in the old thread, it hangs.
>> Even if the new process completes fgetc(), because characters are received,
>> the old process won't get any further.
>
>I suppose that only one thread at a time can read characters from a serial
>port. When a thread wants to read, it probably has to obtain a mutex, then it
>checks a condition such as input buffer not empty or waits on a condition
>variable bound to this condition. When some characters come in, the condition
>variable gets signalled and the thread with the higher priority runs and
>consumes the available characters. Therefore, another thread with a lower
>priority will never get a chance to see a non-empty buffer, or in one word:
>starvation.

You are obviously right, but:

My sscanf() does access a *string*, which is absolutely not related to the
*serial port* read by fgetc().

Peter