Greetings lock wizards
I have discovered some things that I don't understand.
First, if I create a spin-lock in the ".data" segment it
doesn't work on a SMP machine with two CPUs. I know I am
supposed to use the macros, but I have some high-speed stuff
written in assembly that needs a spin-lock. The 'doesn't work'
is that the spin-lock seems to dead-lock, i.e., they loop
forever with the interrupts disabled. I think what's really
happening is that .data was paged and can't be paged back in
with the interrupts off. I don't know. This stuff used to
work....
In earlier versions of Linux, the locks were in .text_lock.
Now they are in : _text_lock_KBUILD_BASENAME
So, what is special about this area that allows locks to work?
And, what is special about .data that prevents them from working?
Also, there is a potential bug (ducks and hides under the desk) in
the existing spin-lock unlocking. To unlock, the lock is simply
set to 1. This works if you have two CPUs, but what about more?
Shouldn't the lock/unlock just be incremented/decremented so 'N' CPUs
can pound on it?
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Windows-2000/Professional isn't.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue May 14 2002 - 12:00:13 EST