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Re: Problem with semaphore_wait & its correct usage.

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Re: Problem with semaphore_wait & its correct usage.

Subject: Re: Problem with semaphore_wait & its correct usage.
From: Terry Lambert <email@hidden>
Date: Mon, 6 Aug 2007 20:32:22 -0700

On Aug 6, 2007, at 8:01 PM, JanakiRam wrote:

         I'm writing a kext driver , using semaphore calls. My
application is hanging when the semaphore_wait is executed.

You need to read Chapter 15 of the Kernel Programming Guide: Semaphores. It's located here:

<http://developer.apple.com/documentation/Darwin/Conceptual/KernelProgramming/synchronization/chapter_15_section_2.html >

Obvious errors:

- Your start/stop functions incorrectly return success when they shouldn't. - The semaphore may not be initialized - You may permit an unload while the PC for some thread is still in the KEXT (panic)

-	You're sleeping a different semaphore than you wake up

Have you considered using an IOCommandQueue or IOCommandGate instead?

<http://developer.apple.com/documentation/Darwin/Reference/KernelIOKitFramework/IOCommandGate/Classes/IOCommandGate/CompositePage.html >

-- Terry

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  >Problem with semaphore_wait & its correct usage. (From: JanakiRam <email@hidden>)




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