Re: [RFC 0/3] aio-posix: call ->poll_end() when removing AioHandler

[Hanna Czenczek]

On 02.01.24 16:24, Hanna Czenczek wrote:

[...]

> I’ve attached the preliminary patch that I didn’t get to send (or test 
> much) last year.  Not sure if it has the same CPU-usage-spike issue 
> Fiona was seeing, the only functional difference is that I notify the 
> vq after attaching the notifiers instead of before.

It’ll take me some more time to send a patch mail to that effect, 
because now there’s an assertion failure on hotunplug, which bisects 
back to eaad0fe26050c227dc5dad63205835bac4912a51 (“scsi: only access 
SCSIDevice->requests from one thread”):

{"execute":"device_del","arguments":{"id":"stg0"}}
{"return": {}}
qemu-system-x86_64: ../block/block-backend.c:2429: blk_get_aio_context: 
Assertion `ctx == blk->ctx' failed.

(gdb) bt
#0  0x00007f32a668d83c in  () at /usr/lib/libc.so.6
#1  0x00007f32a663d668 in raise () at /usr/lib/libc.so.6
#2  0x00007f32a66254b8 in abort () at /usr/lib/libc.so.6
#3  0x00007f32a66253dc in  () at /usr/lib/libc.so.6
#4  0x00007f32a6635d26 in  () at /usr/lib/libc.so.6
#5  0x0000556e6b4880a4 in blk_get_aio_context (blk=0x556e6e89ccf0) at 
../block/block-backend.c:2429
#6  blk_get_aio_context (blk=0x556e6e89ccf0) at 
../block/block-backend.c:2417
#7  0x0000556e6b112d87 in scsi_device_for_each_req_async_bh 
(opaque=0x556e6e2c6d10) at ../hw/scsi/scsi-bus.c:128
#8  0x0000556e6b5d1966 in aio_bh_poll (ctx=ctx@entry=0x556e6d8aa290) at 
../util/async.c:218
#9  0x0000556e6b5bb16a in aio_poll (ctx=0x556e6d8aa290, 
blocking=blocking@entry=true) at ../util/aio-posix.c:722
#10 0x0000556e6b4564b6 in iothread_run 
(opaque=opaque@entry=0x556e6d89d920) at ../iothread.c:63
#11 0x0000556e6b5bde58 in qemu_thread_start (args=0x556e6d8aa9b0) at 
../util/qemu-thread-posix.c:541
#12 0x00007f32a668b9eb in  () at /usr/lib/libc.so.6
#13 0x00007f32a670f7cc in  () at /usr/lib/libc.so.6