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Problem with read data from serial device

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Top Forums Programming Problem with read data from serial device
# 8  
Old 03-06-2010
Quote:
Originally Posted by Corona688

Never call printf from a signal handler. fprintf(stderr, "stuff"); might work since that's unbuffered but even that is not guaranteed. Use write(), along with sprintf if necessary.
For the sake of completeness, it's a bad idea to call fprintf() in a signal handler if the interrupted code also calls fprintf() on the same stream.

Indeed, fprintf() may uses mutex to lock the stream. If it occurs that the signal interrupts fprintf() after it locked the mutex, and fprintf() is called in the signal handler. Well, it's game over: fprintf() shall try to grab again the mutex, and on many implementation this results a deadlock.

Loïc.
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LEARN ABOUT ULTRIX

dc

dc(4)							     Kernel Interfaces Manual							     dc(4)

Name
       dc - serial line/mouse/keyboard

Syntax
       device	 dc0  at ibus?	vector dcintr

Description
       The  serial line controller provides four ports, with modem control on two of the ports.  The DECstation 3100 and DECstation 2100 only pro-
       vide partial modem control.  The DECstation 5000 provides full modem control. The ports are used as follows:

       Port	 Usage
       0	 Graphics device keyboard at 4800 BPS
       1	 Mouse or tablet at 4800 BPS
       2	 Communications port 1 (w/modem control)/local terminal
       3	 Communications port 2 (w/modem control)/local terminal

       Each communication port from the serial line controller behaves as described in and can be set to run at any of 16 speeds.  For the  encod-
       ing, see

       When  a	graphics device is not being used as the system console, communications port 2 becomes the system console.  In this configuration,
       the port can only be used at 9600 BPS and no modem control is supported.

       The serial line driver operates in interrupt-per-character mode (all pending characters are flushed from the silo on each interrupt).

Restrictions
       Speed must be set to 9600 BPS on the console port and 4800 BPS on ports used by graphics devices.  The serial  line  driver  enforces  this
       restriction; that is, changing speeds with the command may not always work on these ports.

Files
       console terminal

       local terminal

       local terminal

See Also
       console(4), devio(4), tty(4), ttys(5), MAKEDEV(8)

								       RISC								     dc(4)