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[ipsp]

I'm trying to write a small program to demostrate two threads writing to a file. I protect simaltenous writes to the file with a semaphore, but unfortunately I'm get some weird result.

Can anyone tell me if the following is correct

<pre>

void init_Dbug()
{
_writeSema = sceKernelCreateSema("_writeSema", 0, 0, 1, 0);
}

void write_DBug(const char * const text)
{
sceKernelWaitSema(_writeSema, 0, 0);
sceKernelSignalSema(_writeSema, 1);

fprintf(_dBugFile, text);
fflush(_dBugFile);

sceKernelSignalSema(_writeSema, 0);
}

</pre>


Ooutput file, note that 'thread 1' first write is missing, and that the 'newline' character is missing in one case.

<pre>

Thread [2] idx [0]
Thread [1] idx [1]
Thread [2] idx [1]
Thread [1] idx [2]
Thread [2] idx [2]
Thread [1] idx [3]
Thread [2] idx [3]
Thread [1] idx [4]
Thread [2] idx [4]
Thread [1] idx [5]
Thread [2] idx [5]
Thread [1] idx [6]
Thread [2] idx [6]
Thread [1] idx [7]Thread [2] idx [7]
Thread [1] idx [8]
Thread [2] idx [8]
Thread [1] idx [9]
Thread [2] idx [9]
Thread [1] idx [10]
Thread [2] idx [10]

</pre>

Does anyone know if my semaphore code is correct, and if it is why the output file seems to get incorrect data.

[PeterM]

Here's how I've done it, and it seems to work correctly:

// Create the mutex.
SceUID mutex = sceKernelCreateSema("myMutexName", 0, 1, 1, 0);

// Wait until the mutex is available. (Implicitly decrements its value)
sceKernelWaitSema(mutex, 1, 0);

// Do your protected stuff here...

// Unlock the mutex.
sceKernelSignalSema(mutex, 1);

Hope this helps, please someone correct me if it's not right.

Pete

[ipsp]

[PeterM]

A few of the PSPSDK functions seem to take or return ints when there are appropriate enums or other types.

I guess it doesn't matter too much.

Anyway, the thing that confused me when trying semaphores for the first time was that waiting for one implicitly subtracted 1 from its value, so if you wait for it to become "1", when you get it, it will then be "0".

Then when you're done, you signal it, adding 1 to it, to make it "1" again. Then anyone else waiting for it to be "1" will get it.

Hope it helped.

[ipsp]

[urchin]