[ltt-dev] UST use case: Tracing QEMU/KVM

[pierre-marc.fournier@polymtl.ca (Pierre-Marc Fournier)]

Stefan Hajnoczi wrote:
> /*
>  * This example demonstrates the UST listener thread receiving signals and
>  * returning from poll().
>  *
>  * $ gcc -o poll_eintr poll_eintr.c -lust -lpthread
>  * $ ./poll_eintr
>  * main thread id=0x7f9c31a766a0
>  * ^CSIGINT handled in thread id=0x7f9c30ed7910
>  * libust[2615/2616]: Error: poll: Interrupted system call (in multipoll_poll() at ../libustcomm/multipoll.c:84)
>  * libust[2615/2616]: Error: error in multipoll_poll (in listener_main() at tracectl.c:1015)
>  *
>  * This happens because all other threads have SIGINT blocked, whereas libust
>  * does not block signals in the client thread.  Therefore the signal is
>  * handled in the client thread, poll() is interrupted, and an error is
>  * printed.
>  *
>  * I think the correct behavior is to block signals in the client thread so it
>  * will not interfere with signal handling of the main program.
>  */

I completely agree. I just pushed a change that blocks all signals in 
the listener thread.

Thanks!