On Thu, May 14, 2020 at 03:34:24PM +0800, Jason Wang wrote: > > On 2020/5/13 下午5:47, Dima Stepanov wrote: > >>> case CHR_EVENT_CLOSED: > >>> /* a close event may happen during a read/write, but vhost > >>> * code assumes the vhost_dev remains setup, so delay the > >>> * stop & clear to idle. > >>> * FIXME: better handle failure in vhost code, remove bh > >>> */ > >>> if (s->watch) { > >>> AioContext *ctx = qemu_get_current_aio_context(); > >>> > >>> g_source_remove(s->watch); > >>> s->watch = 0; > >>> qemu_chr_fe_set_handlers(&s->chr, NULL, NULL, NULL, NULL, > >>> NULL, NULL, false); > >>> > >>> aio_bh_schedule_oneshot(ctx, chr_closed_bh, opaque); > >>> } > >>> break; > >>> > >>>I think it's time we dropped the FIXME and moved the handling to common > >>>code. Jason? Marc-André? > >>I agree. Just to confirm, do you prefer bh or doing changes like what is > >>done in this series? It looks to me bh can have more easier codes. > >Could it be a good idea just to make disconnect in the char device but > >postphone clean up in the vhost-user-blk (or any other vhost-user > >device) itself? So we are moving the postphone logic and decision from > >the char device to vhost-user device. One of the idea i have is as > >follows: > > - Put ourself in the INITIALIZATION state > > - Start these vhost-user "handshake" commands > > - If we got a disconnect error, perform disconnect, but don't clean up > > device (it will be clean up on the roll back). I can be done by > > checking the state in vhost_user_..._disconnect routine or smth like it > > > Any issue you saw just using the aio bh as Michael posted above. > > Then we don't need to deal with the silent vhost_dev_stop() and we will have > codes that is much more easier to understand. I've implemented this solution inside hw/block/vhost-user-blk.c:vhost_user_blk_event() in the similar way by using the s->connected field. Looks good and more correct fix ). I have two questions here before i'll rework the fixes: 1. Is it okay to make the similar fix inside vhost_user_blk_event() or we are looking for more generic vhost-user solution? What do you think? 2. For migration we require an additional information that for the vhost-user device it isn't an error, because i'm trigerring the following assert error: Core was generated by `x86_64-softmmu/qemu-system-x86_64 -nodefaults -no-user-config -M q35,sata=false'. Program terminated with signal SIGABRT, Aborted. #0 0x00007fb56e729428 in raise () from /lib/x86_64-linux-gnu/libc.so.6 [Current thread is 1 (Thread 0x7fb486ef5700 (LWP 527734))]
(gdb) bt #0 0x00007fb56e729428 in raise () from /lib/x86_64-linux-gnu/libc.so.6 #1 0x00007fb56e72b02a in abort () from /lib/x86_64-linux-gnu/libc.so.6 #2 0x00005648ea376ee6 in vhost_log_global_start (listener=0x5648ece4eb08) at ./hw/virtio/vhost.c:857 #3 0x00005648ea2dde7e in memory_global_dirty_log_start () at ./memory.c:2611 #4 0x00005648ea2e68e7 in ram_init_bitmaps (rs=0x7fb4740008c0) at ./migration/ram.c:2305 #5 0x00005648ea2e698b in ram_init_all (rsp=0x5648eb1f0f20 <ram_state>) at ./migration/ram.c:2323 #6 0x00005648ea2e6cc5 in ram_save_setup (f=0x5648ec609e00, opaque=0x5648eb1f0f20 <ram_state>) at ./migration/ram.c:2436 #7 0x00005648ea67b7d3 in qemu_savevm_state_setup (f=0x5648ec609e00) at migration/savevm.c:1176 #8 0x00005648ea674511 in migration_thread (opaque=0x5648ec031ff0) at migration/migration.c:3416 #9 0x00005648ea85d65d in qemu_thread_start (args=0x5648ec6057f0) at util/qemu-thread-posix.c:519 #10 0x00007fb56eac56ba in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0 #11 0x00007fb56e7fb41d in clone () from /lib/x86_64-linux-gnu/libc.so.6 (gdb) frame 2 #2 0x00005648ea376ee6 in vhost_log_global_start (listener=0x5648ece4eb08) at ./hw/virtio/vhost.c:857 857 abort(); (gdb) list 852 { 853 int r; 854 855 r = vhost_migration_log(listener, true); 856 if (r < 0) { 857 abort(); 858 } 859 } 860 861 static void vhost_log_global_stop(MemoryListener *listener) Since bh postphone the clean up, we can't use the ->started field. Do we have any mechanism to get the device type/state in the common vhost_migration_log() routine? So for example for the vhost-user/disconnect device we will be able to return 0. Or should we implement it and introduce it in this patch set? Thanks, Dima. > > Thank > > > > - vhost-user command returns error back to the _start() routine > > - Rollback in one place in the start() routine, by calling this > > postphoned clean up for the disconnect > > >