About NtWaitForAlertByThreadId and NtAlertThreadByThreadId
CarterLi opened this issue · 8 comments
我看到 AcquireSRWLockExclusive 和 SleepConditionVariableSRW 都是用 NtWaitForAlertByThreadId
https://github.com/processhacker/processhacker/blob/master/phnt/include/ntpsapi.h#L1656
关于SRWLock不支持timed_mutex的问题，NtWaitForAlertByThreadId 本身支持 timeout，只是 AcquireSRWLockExclusive 没开放出来
NtWaitForAlertByThreadId 比 NtWaitForKeyedEvent 参数更少，功能更专用，性能应该会比后者好
包括 rpcs3 也是优先 NtWaitForAlertByThreadId ：https://github.com/valgusk/rpcs3-old-rpcn/blob/f6f12b3b0dfeedc260d44e3be713fcb03c9638eb/rpcs3/util/atomic.cpp#L1192
考虑一下？
That is a completely different thing. As there is no longer a 'key', it will be necessary to perform some bookkeeping in user mode.
One possible design for reducing bus pressure is to allocate a structure on the stack and use it to build a wait queue. This answers why SRWLOCK doesn't support timeouts: It is not safe to remove nodes from wait queues without global locking, otherwise a thread that attempts to wake up another one which has timed out would reference destroyed objects and cause unpredictable results.
这个东西我是外行。说的有错不要介意。
That is a completely different thing. As there is no longer a 'key', it will be necessary to perform some bookkeeping in user mode.
NtWaitForAlertByThreadId，这里的ThreadId不就是这个key？
No there is no thread ID argument. This function suspends the current thread for the timeout specified by its second argument. See https://source.winehq.org/source/dlls/ntdll/sync.c#0931 for example.
No there is no thread ID argument. This function suspends the current thread for the timeout specified by its second argument. See https://source.winehq.org/source/dlls/ntdll/sync.c#0931 for example.
You can only suspend the current thread, so you don't need to pass the thread ID argument in ( like what Sleep does ). It's enough, isn't it?
Then when a thread attempts to unlock a mutex, how does it know which threads are currently waiting, and which one it should wake up?
Isn't it (thread id) stored in the mutex object?
So a mutex object must maintain a wait queue. I understood.
What is address used for? According to the implementation of wine, address is completely unused ( only for tracing ).
It's unused in Wine. Not sure about Windows.