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c89d1c879a
QEMU has a per-thread "bql_locked" variable stored in TLS section, showing whether the current thread is holding the BQL lock. It's a pretty handy variable. Function-wise, QEMU have codes trying to conditionally take bql, relying on the var reflecting the locking status (e.g. BQL_LOCK_GUARD), or in a GDB debugging session, we could also look at the variable (in reality, co_tls_bql_locked), to see which thread is currently holding the bql. When using that as a debugging facility, sometimes we can observe multiple threads holding bql at the same time. It's because QEMU's condvar APIs bypassed the bql_*() API, hence they do not update bql_locked even if they have released the mutex while waiting. It can cause confusion if one does "thread apply all p co_tls_bql_locked" and see multiple threads reporting true. Fix this by moving the bql status updates into the mutex debug hooks. Now the variable should always reflect the reality. Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Message-ID: <20250904223158.1276992-1-peterx@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
62 lines
1.4 KiB
C
62 lines
1.4 KiB
C
/*
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* Common qemu-thread implementation header file.
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*
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* Copyright Red Hat, Inc. 2018
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*
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* Authors:
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* Peter Xu <peterx@redhat.com>,
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#ifndef QEMU_THREAD_COMMON_H
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#define QEMU_THREAD_COMMON_H
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#include "qemu/thread.h"
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#include "qemu/main-loop.h"
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#include "trace.h"
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static inline void qemu_mutex_post_init(QemuMutex *mutex)
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{
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#ifdef CONFIG_DEBUG_MUTEX
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mutex->file = NULL;
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mutex->line = 0;
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#endif
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mutex->initialized = true;
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}
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static inline void qemu_mutex_pre_lock(QemuMutex *mutex,
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const char *file, int line)
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{
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trace_qemu_mutex_lock(mutex, file, line);
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}
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static inline void qemu_mutex_post_lock(QemuMutex *mutex,
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const char *file, int line)
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{
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#ifdef CONFIG_DEBUG_MUTEX
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mutex->file = file;
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mutex->line = line;
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#endif
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trace_qemu_mutex_locked(mutex, file, line);
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if (mutex_is_bql(mutex)) {
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bql_update_status(true);
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}
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}
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static inline void qemu_mutex_pre_unlock(QemuMutex *mutex,
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const char *file, int line)
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{
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#ifdef CONFIG_DEBUG_MUTEX
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mutex->file = NULL;
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mutex->line = 0;
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#endif
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trace_qemu_mutex_unlock(mutex, file, line);
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if (mutex_is_bql(mutex)) {
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bql_update_status(false);
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}
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}
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#endif
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