62aa1d887f
@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>
51 lines
1.6 KiB
C
51 lines
1.6 KiB
C
#ifndef MONITOR_H
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#define MONITOR_H
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#include "qemu-common.h"
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#include "block/block.h"
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#include "qapi/qapi-types-misc.h"
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#include "qemu/readline.h"
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extern __thread Monitor *cur_mon;
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/* flags for monitor_init */
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/* 0x01 unused */
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#define MONITOR_USE_READLINE 0x02
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#define MONITOR_USE_CONTROL 0x04
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#define MONITOR_USE_PRETTY 0x08
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#define MONITOR_USE_OOB 0x10
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bool monitor_cur_is_qmp(void);
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void monitor_init_globals(void);
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void monitor_init(Chardev *chr, int flags);
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void monitor_cleanup(void);
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int monitor_suspend(Monitor *mon);
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void monitor_resume(Monitor *mon);
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int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp);
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int monitor_fd_param(Monitor *mon, const char *fdname, Error **errp);
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void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
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GCC_FMT_ATTR(2, 0);
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void monitor_printf(Monitor *mon, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
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int monitor_fprintf(FILE *stream, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
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void monitor_flush(Monitor *mon);
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int monitor_set_cpu(int cpu_index);
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int monitor_get_cpu_index(void);
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void monitor_read_command(Monitor *mon, int show_prompt);
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int monitor_read_password(Monitor *mon, ReadLineFunc *readline_func,
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void *opaque);
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AddfdInfo *monitor_fdset_add_fd(int fd, bool has_fdset_id, int64_t fdset_id,
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bool has_opaque, const char *opaque,
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Error **errp);
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int monitor_fdset_get_fd(int64_t fdset_id, int flags);
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int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd);
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void monitor_fdset_dup_fd_remove(int dup_fd);
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int monitor_fdset_dup_fd_find(int dup_fd);
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#endif /* MONITOR_H */
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