BUG REPORT: aio with fork

[Szabolcs Nagy]

On 13/07/16 18:51, Rajat Kateja wrote:
> Hi,
> 
> I think I have hit a bug in the AIO system. I contacted the linux-aio
> mailing list but was redirected here because I am using posix-aio.
> Please see the following bug report:
> 
> One line description: Doing AIO concurrently before and after a fork
> causes the IOs after the fork to be never queued.
> 
> Full Description: Consider the scenario.
> 
> 1. A program issues an aio_read/aio_write
> 2. After the completion of the aio, the program forks
> 3. The child process issues an aio_read/aio_write
> 
> The aio code (from aio_misc.c) maintains a global variable
> idle_thread_count. Also, aio threads idle for a period of 1 second (by
> default) after completing the IO operation. During this one second,
> the parent forks and the child gets the copy of the idle_thread_count
> from the global data segment. When the child issues a fresh aio
> request, the code sees that the idle_thread_count is greater than one
> and signals a condition variable to wake up the thread. But of course,
> there if no thread in the child process. Hence the AIO stays in the
> EINPROGRESS state forever.
> 

submit the bug report at https://sourceware.org/bugzilla
so ppl can keep track of it.

(i believe the aio design in musl libc does not have this problem.)