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Date:	Wed, 7 Mar 2012 15:59:35 -0500
Message-ID:	<CAG_2cTm5JXFsiK0MaUQr36pxVFNeAmsNpGTo65q9inRB=U5e4w@mail.gmail.com>
Subject:	Re: Anamoly with ioctl() in cygwin 1.7.10
From:	Jon Clugston <jon DOT clugston AT gmail DOT com>
To:	cygwin AT cygwin DOT com
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On Wed, Mar 7, 2012 at 1:51 PM, Lee Collier wrote:
> Hello,
>
> I'm new to cygwin and ran into an anamoly with calling ioctl() that
> I've not experienced on Linux. It appears that ioctl() behaves as
> expected when it is called from the main thread; however, it does not
> when called from a thread created by the main thread. Is this expected
> behavior when using cygwin?
>
> I've added a sample program to demonstrate the anomaly. The call to
> listInterfaces() from main() will function properly. The call to
> listInterfaces() from handlePackets() will fail at ioctl(sck,
> SIOCGIFCONF, &ifc); however, the errno result reported by perror is
> "No error".
>
> Regards,
> LC
>
> #include <sys/ioctl.h>
> #include <net/if.h>
> #include <netinet/in.h>
> #include <stdio.h>
> #include <arpa/inet.h>
> #include <pthread.h>
>
> int listInterfaces(void);
> void* handlePackets (void* data);
>
> int main(void)
> {
>   pthread_t pktHandlerThreadId;
>   pthread_mutex_t pktMutex;
>
>   printf("Result from main thread:\n");
>   listInterfaces();
>   pthread_mutex_lock(&pktMutex);

Don't know if it will fix your problem, but you cannot just create a
mutex on the stack and call "lock" on it.  You must initialize it with
"pthread_mutex_init()".



Jon

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