On 03/22/13 22:39, Luiz Capitulino wrote: > On Fri, 22 Mar 2013 16:50:39 -0400 > Luiz Capitulino <lcapitul...@redhat.com> wrote: > >> On Fri, 22 Mar 2013 10:17:58 +0100 >> KONRAD Frédéric <fred.kon...@greensocs.com> wrote: >> >>> Hi, >>> >>> Seems there is an issue with the current git (found by toddf on IRC). >>> >>> To reproduce: >>> >>> ./qemu-system-x86_64 --monitor stdio --nographic >>> >>> and put "?" it should abort. >>> >>> Here is the backtrace: >>> >>> #0 0x00007f77cd347935 in raise () from /lib64/libc.so.6 >>> #1 0x00007f77cd3490e8 in abort () from /lib64/libc.so.6 >>> #2 0x00007f77cd3406a2 in __assert_fail_base () from /lib64/libc.so.6 >>> #3 0x00007f77cd340752 in __assert_fail () from /lib64/libc.so.6 >>> #4 0x00007f77d1c1f226 in monitor_puts (mon=<optimized out>, >>> str=<optimized out>) at >> >> Yes, it's easy to reproduce. Bisect says: >> >> f628926bb423fa8a7e0b114511400ea9df38b76a is the first bad commit >> commit f628926bb423fa8a7e0b114511400ea9df38b76a >> Author: Gerd Hoffmann <kra...@redhat.com> >> Date: Tue Mar 19 10:57:56 2013 +0100 >> >> fix monitor >> >> chardev flow control broke monitor, fix it by adding watch support. >> >> Signed-off-by: Anthony Liguori <aligu...@us.ibm.com> >> >> My impression is that monitor_puts() in being called in parallel. > > Not all. > > What's happening is that qemu_chr_fe_write() is returning < 0, > mon->outbuf_index is not reset and is full, this causes the assert in > monitor_puts() to trig. > > The previous version of monitor_flush() ignores errors, and everything > works, so doing the same thing here fixes the problem :)
No, ignoring errors breaks qmp because the output isn't valid json any more when you cut off something ... > For some reason I'm unable to see what the error code is. Gerd, do you think > the patch below is reasonable? If it's not, how should we handle errors here? No, it's not. Ignoring the error for errno = EAGAIN breaks flow control. Ignoring the error for errno != EAGAIN (and maybe logging a debug message) would be ok, but I suspect it's actually EAGAIN you get here. Just go for a larger buffer? cheers, Gerd
