On 03/10/2011 02:45 PM, Anthony Liguori wrote:
On 03/10/2011 07:06 AM, Paolo Bonzini wrote:
On 03/10/2011 01:59 PM, Corentin Chary wrote:
Instead, we now store the data in a temporary buffer, and use a socket
pair to notify the main thread that new data is available.
You can use a bottom half for this instead of a special socket.
Signaling a bottom half is async-signal- and thread-safe.
Bottom halves are thread safe?
I don't think so.
They probably should be but they aren't today.
Creating a new bottom half is not thread-safe, but scheduling one is.
Assuming that you never use qemu_bh_schedule_idle, qemu_bh_schedule
boils down to:
if (bh->scheduled)
return;
bh->scheduled = 1;
/* stop the currently executing CPU to execute the BH ASAP */
qemu_notify_event();
You may have a spurious wakeup if two threads race on the same bottom
half (including the signaling thread racing with the IO thread), but
overall you can safely treat them as thread-safe.
Paolo
