Hi!
As Glynn Clements noted yesterday many useful functions can't be safely
called from within a signal handler because of their non-reentrant nature.
The problem is - how to handle cleanup code when the program is not "event
driven" so there is no event-loop all of the time (for instance u are
SIGINT-ed during a heavy computation).
Also - I/O calls are non-atomic (when dealing with data sizes over the
guaranteed atomic size which is 512 bytes for pipes by POSIX and 4096
bytes in Linux, not sure for other calls) and they may be interrupted by
signal. So u either check for EINTR (inconvinient) or use
TEMP_FAILURE_RETRY macro , or set the SA_RESTART flag in sigaction().
And my question is - what happens when a SIGINT / SIGKILL arrives and
interrupts the I/O call - will TEMP_FAILURE_RETRY be evaluated again as when
the above signals arrive the process will never switch back task mode
(this may be no problem if the SA_RESTART flag is set as it doesn't imply
a swith to task mode, it will just resume the I/O primitive in kernel
mode)
Thanx for the help!
Marin
-= Why do we need gates in a world without fences? =-
