qemu-e2k/include
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
..
block block: Use uint64_t for BdrvTrackedRequest byte fields 2018-07-10 16:01:52 +02:00
chardev chardev: comment details for CLOSED event 2018-06-30 17:50:48 +02:00
crypto crypto: Implement TLS Pre-Shared Keys (PSK). 2018-07-03 13:04:38 +01:00
disas RISC-V Disassembler 2018-03-07 08:30:28 +13:00
exec * IEC units series (Philippe) 2018-07-02 19:07:19 +01:00
fpu fpu/softfloat: Specialize on snan_bit_is_one 2018-05-17 15:27:15 -07:00
hw Bug fixes. 2018-07-17 17:06:32 +01:00
io qio: non-default context for TLS handshake 2018-03-06 10:19:07 +00:00
libdecnumber Clean up ill-advised or unusual header guards 2016-07-12 16:20:46 +02:00
migration typedefs: add QJSON 2018-06-15 14:40:56 +01:00
monitor monitor: Fix unsafe sharing of @cur_mon among threads 2018-07-23 14:00:03 +02:00
net net: Remove the deprecated "vlan" parameter 2018-05-14 15:47:14 +08:00
qapi qmp: Use QDict * instead of QObject * for response objects 2018-07-03 23:18:56 +02:00
qemu cutils: Do not include "qemu/units.h" directly 2018-07-02 15:41:17 +02:00
qom qom/object: Add a new function object_initialize_child() 2018-07-17 13:12:49 +01:00
scsi pr-manager: add query-pr-managers QMP command 2018-06-28 19:05:35 +02:00
standard-headers linux-headers: Update to kernel mainline commit b357bf602 2018-06-22 13:28:35 +01:00
sysemu Revert "block: Remove deprecated -drive geometry options" 2018-07-10 14:36:12 +02:00
ui Add gles support to egl-helpers, wire up in egl-headless and gtk. 2018-06-26 13:48:49 +02:00
elf.h linux-user: ARM-FDPIC: Identify ARM FDPIC binaries 2018-05-03 18:25:29 +02:00
glib-compat.h glib: enforce the minimum required version and warn about old APIs 2018-06-29 12:22:28 +01:00
qemu-common.h qemu-options: Bail out on unsupported options instead of silently ignoring them 2018-05-09 00:13:39 +02:00
qemu-io.h qemu-io: Let command functions return error code 2018-06-11 16:18:45 +02:00
trace-tcg.h trace: get rid of generated-events.h/generated-events.c 2016-10-12 09:54:52 +02:00