Watch point issue across multiple threads

Hi All,

I have set a watch-point to monitor the contents changing in global data 
address. The data in this global address is accessed & modified by 3 
threads.

*(gdb)watch *(int *) 0xb75dafd8*

But now I get the following warning each time a thread is started or 
when a thread stops:

*warning:  Could not remove hardware watchpoint 2*

Please let me know the reason why watch-point get affected by thread 
exit. However I do not want the watch-point to be removed. What do I 
have to do such
that gdb does not try to remove the watch-point & watch-point can be 
used by multiple threads? Please guide me.

Thanks & Best Regards,
Vinay