On Fri, Oct 08, 2004 at 10:03:50PM +0530, Vinu V wrote: > > Thanks Jason for the reply. > > But why is this considered not safe. Could this be a little more elaborated ?
Asynchronous signal handlers can be executed at any time. This means that you could be part way through locking a mutex in normal (non-signal handler) code, then jump into the signal handler. You might succeed in locking the mutex in the signal handler, but the normal code assumed that the mutex lock operation was atomic, and the signal handler has gone and messed with the mutex behind the normal code's back. Havoc ensues. Pth does not protect against signal handlers in such critical sections of code (mutex locking in this example), because the overhead would be prohibitively expensive. It is your responsibility not to do anything dangerous in the signal handler. In general, threads and signals do not mix well. In practice, it s often necessary to use both, but doing so is a delicate dance. You would be well advised to read a book that covers this issue in some detail. My favorite is "Programming with POSIX Threads", by David Butenhof. Jason ______________________________________________________________________ GNU Portable Threads (Pth) http://www.gnu.org/software/pth/ Development Site http://www.ossp.org/pkg/lib/pth/ Distribution Files ftp://ftp.gnu.org/gnu/pth/ Distribution Snapshots ftp://ftp.ossp.org/pkg/lib/pth/ User Support Mailing List [EMAIL PROTECTED] Automated List Manager (Majordomo) [EMAIL PROTECTED]
