Can multi-threads wait for a same event?

NTDEV
1

Can multi-threads wait for a same event? Thread1-3 call KeWaitForSingleObject to wait the same event, thread 4 will call KeSetEvent to set the event signal, then, If the thread1-3 can be wake up at the same time?

2

Yes if it is a notification event. Once signaled, a notification event remains signaled until explicitly cleared. A synchronization event on the other hand will only wake up one thread and reset back to a clear state once a wait has been satisfied (and in your scenario, it is not defined which thread 1-3 will actually wake up with a sync event)

d

-----Original Message-----
From: xxxxx@lists.osr.com [mailto:xxxxx@lists.osr.com] On Behalf Of xxxxx@yahoo.com.cn
Sent: Thursday, April 08, 2010 10:47 PM
To: Windows System Software Devs Interest List
Subject: [ntdev] Can multi-threads wait for a same event?

Can multi-threads wait for a same event? Thread1-3 call KeWaitForSingleObject to wait the same event, thread 4 will call KeSetEvent to set the event signal, then, If the thread1-3 can be wake up at the same time?

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3

Thanks Doron Holan! It seems I need use the notification event.

4

As you said,it is a notification event, the thread1-3 will be wake up when thread4 signal the event.

Thread should set the event to be non-signal manually if the it is notification event(event will be set to non-signal automatically if call KeWaitForSingleObject again if it is synchronization event ).

Now, three threads share the same notification event,if the event that per-thread uses will be no-signal only one thread set it to no-signal?

5

I do not understand your question

d

tiny phone keyboard + fat thumbs = you do the muth

-----Original Message-----
From: xxxxx@yahoo.com.cn
Sent: Friday, April 09, 2010 12:18 AM
To: Windows System Software Devs Interest List
Subject: RE:[ntdev] Can multi-threads wait for a same event?

As you said,it is a notification event, the thread1-3 will be wake up when thread4 signal the event.

Thread should set the event to be non-signal manually if the it is notification event(event will be set to non-signal automatically if call KeWaitForSingleObject again if it is synchronization event ).

Now, three threads share the same notification event,if the event that per-thread uses will be no-signal only one thread set it to no-signal?

—
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6

"Now, three threads share the same notification event,if the event that per-thread uses will be no-signal only one thread set it to no-signal? "

That depends?on your logic.?All it?says is the notification event will remain signaled until someone clears it. So you may have multiple threads clear it multiple times. If that leads to a race?condition, you will need to?utlize?other?synchronization??primitives in combination with the syhncronization event.

Lijun

From: “xxxxx@yahoo.com.cn”
To: Windows System Software Devs Interest List
Sent: Fri, April 9, 2010 3:17:50 AM
Subject: RE:[ntdev] Can multi-threads wait for a same event?

As you said,it is a notification event, the thread1-3 will be wake up when thread4 signal the event.

Thread should set the event to be non-signal manually if the it is notification event(event will be set to non-signal automatically if call KeWaitForSingleObject again if it is synchronization event ).

Now, three threads share the same notification event,if the event that per-thread uses will be no-signal only one thread set it to no-signal?

—
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7

xxxxx@yahoo.com.cn wrote:

As you said,it is a notification event, the thread1-3 will be wake up when thread4 signal the event.

Thread should set the event to be non-signal manually if the it is notification event(event will be set to non-signal automatically if call KeWaitForSingleObject again if it is synchronization event ).

Yes.

Now, three threads share the same notification event,if the event that per-thread uses will be no-signal only one thread set it to no-signal?

Kernel events are not per-thread. They are global. If one thread
clears the event, then the event becomes non-signaled, and the next
thread to wait on it will block.

–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.

8

> Can multi-threads wait for a same event? Thread1-3 call KeWaitForSingleObject to wait the same

event, thread 4 will call KeSetEvent to set the event signal, then, If the thread1-3 can be wake up at the
same time?

For NotificationEvent, all 3 threads are awaken, and will run sooner or later. The event remains signaled.

For SynchronizationEvent, only 1 of the threads is awaken, and the event remains unsignaled.

–
Maxim S. Shatskih
Windows DDK MVP
xxxxx@storagecraft.com
http://www.storagecraft.com