On Mon, Mar 04, 2013 at 04:32:13PM +0100, Sander Smeenk wrote: > So, it's not a fork() from the main process (which would perhaps > copy all threads to the fork()ed process, or maybe not, who knows).
fork() on linux creates a single thread in the child process, but copies the memory and state of *all* threads. Which is why you can get in a right mess. For example, if one of the other threads had something locked, that will be still be locked in the new process, but without a corresponding thread still running that can unlock it. So the forked process might deadlock or otherwise behave strangely. This is why people say not to mix threads and forks. -- My Dad used to say 'always fight fire with fire', which is probably why he got thrown out of the fire brigade.
