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>
45 lines
727 B
C
45 lines
727 B
C
#include "qemu/osdep.h"
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#include "qemu/main-loop.h"
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static bool bql_is_locked = false;
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static uint32_t bql_unlock_blocked;
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bool bql_locked(void)
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{
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return bql_is_locked;
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}
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void rust_bql_mock_lock(void)
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{
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bql_is_locked = true;
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}
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void bql_lock_impl(const char *file, int line)
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{
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}
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void bql_unlock(void)
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{
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assert(!bql_unlock_blocked);
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}
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void bql_block_unlock(bool increase)
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{
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uint32_t new_value;
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assert(bql_locked());
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/* check for overflow! */
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new_value = bql_unlock_blocked + increase - !increase;
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assert((new_value > bql_unlock_blocked) == increase);
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bql_unlock_blocked = new_value;
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}
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bool mutex_is_bql(QemuMutex *mutex)
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{
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return false;
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}
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void bql_update_status(bool locked)
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{
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}
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