Peter Xu 62aa1d887f monitor: Fix unsafe sharing of @cur_mon among threads ... @cur_mon is null unless the main thread is running monitor code, either HMP code within monitor_read(), or QMP code within monitor_qmp_dispatch(). Use of @cur_mon outside the main thread is therefore unsafe. Most of its uses are in monitor command handlers. These run in the main thread. However, there are also uses hiding elsewhere, such as in error_vprintf(), and thus error_report(), making these functions unsafe outside the main thread. No such unsafe uses are known at this time. Regardless, this is an unnecessary trap. It's an ancient trap, though. More recently, commit cf869d5317 "qmp: support out-of-band (oob) execution" spiced things up: the monitor I/O thread assigns to @cur_mon when executing commands out-of-band. Having two threads save, set and restore @cur_mon without synchronization is definitely unsafe. We can end up with @cur_mon null while the main thread runs monitor code, or non-null while it runs non-monitor code. We could fix this by making the I/O thread not mess with @cur_mon, but that would leave the trap armed and ready. Instead, make @cur_mon thread-local. It's now reliably null unless the thread is running monitor code. Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> [peterx: update subject and commit message written by Markus] Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20180720033451.32710-1-peterx@redhat.com>		2018-07-23 14:00:03 +02:00
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hmp-target.h	Clean up header guards that don't match their file name	2016-07-12 16:19:16 +02:00
monitor.h	monitor: Fix unsafe sharing of @cur_mon among threads	2018-07-23 14:00:03 +02:00
qdev.h	qdev: add function qdev_set_id()	2016-11-22 10:29:37 -08:00