On (Mon) 13 Jun 2016 [05:07:39], Li, Liang Z wrote: > > > > > +static void wait_for_decompress_done(void) { > > > > > + int idx, thread_count; > > > > > + > > > > > + if (!migrate_use_compression()) { > > > > > + return; > > > > > + } > > > > > + > > > > > + thread_count = migrate_decompress_threads(); > > > > > + qemu_mutex_lock(&decomp_done_lock); > > > > > + for (idx = 0; idx < thread_count; idx++) { > > > > > + while (!decomp_param[idx].done) { > > > > > + qemu_cond_wait(&decomp_done_cond, > > &decomp_done_lock); > > > > > + } > > > > > + } > > > > > + qemu_mutex_unlock(&decomp_done_lock); > > > > > > > > Not sure how this works: in the previous patch, done is set to false > > > > under the decomp_done_lock. Here, we take the lock, and wait for done > > to turn false. > > > > That can't happen because this thread holds the lock. > > > > My reading is this is going to lead to a deadlock. What am I missing? > > > > > > > > > > This is the typical usage of the QemuCond, actually, in > > > qemu_cond_wait() , decomp_done_lock will be unlocked at first and then > > > locked again before > > > qemu_cond_wait() return. So deadlock won't happen. > > > > In qemu-thread-posix.c, I don't see such unlock/lock. > > > > > > Amit > > I mean in the 'pthread_cond_wait()' which called by qemu_cond_wait().
Yes, OK - makes sense now. Thanks, I'll continue the review. Amit