Linus Torvalds wrote:
> 
> If the choice is between a hack to do strange and incomprehensible things
> for a special case, and just making the semaphores do the same thing
> rw-spinlocks do and make the problem go away naturally, Ill take #2 any
> day. The patches already exist, after all.
>

I've attached a recursive semaphore patch against 2.4.10-pre11 - but it
makes mmap io unusable:

Testcase:
* file, mmaped, 300 MB, 128 MB Ram
* 2 threads: touch random pages 
* third thread: calls mprotect(0xFFFF00000,0x1000, PAGE_READ)

Result:
mprotect hangs forever (minutes) with recursive semaphores.

With fair semaphores, mprotect returns after ~80 milliseconds with 5
worker threads, after ~380 milliseconds with 20 worker threads (slow IDE
disk).

One alternative to David's patch would be moving the locking into the
coredump handlers - would you prefer that?

--
	Manfred