Re: [PATCH] powerpc vdso updates

* Benjamin Herrenschmidt [off-list ref] wrote:

This patch cleans up some locking & error handling in the ppc vdso and 
moves the vdso base pointer from the thread struct to the mm context 
where it more logically belongs. It brings the powerpc implementation 
closer to Ingo's new x86 one and also adds an arch_vma_name() function 
allowing to print [vsdo] in /proc/<pid>/maps if Ingo's x86 vdso patch 
is also applied.

looks good to me.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Reviewed-by: Ingo Molnar <redacted>

This is 2.6.18 material, hopefully should go along with Ingo's x86 
vdso updates. Ingo, if you change something to arch_vma_name(), please 
let me know.

ok. There's one bit that could potentially be 2.6.17 material:

 	 * at vdso_base which is the "natural" base for it, but we might fail
 	 * and end up putting it elsewhere.
 	 */
+	down_write(&mm->mmap_sem);
 	vdso_base = get_unmapped_area(NULL, vdso_base,
 				      vdso_pages << PAGE_SHIFT, 0, 0);

get_unmapped_area() without holding the mmap semaphore seems dangerous. 
The VDSO setup itself should be 'private' to the process, but i'm not 
totally sure that no other kernel code could get access to this mm. For 
example the swapout code? Am i missing something?

	Ingo