Re: PR/49328 CVS commit: src/sys/dev/pci/ixgbe

[Chuck Silvers <chuq%chuq.com@localhost>]

The following reply was made to PR kern/49328; it has been noted by GNATS.

From: Chuck Silvers <chuq%chuq.com@localhost>
To: Christos Zoulas <christos%zoulas.com@localhost>
Cc: 6bone%6bone.informatik.uni-leipzig.de@localhost, gnats-bugs%NetBSD.org@localhost,
	kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
	netbsd-bugs%netbsd.org@localhost
Subject: Re: PR/49328 CVS commit: src/sys/dev/pci/ixgbe
Date: Sun, 1 Feb 2015 09:33:46 -0800

 On Sun, Feb 01, 2015 at 11:30:57AM -0500, Christos Zoulas wrote:
 > Yes, and my plan is to first fix the NOSLEEP allocation issues and then
 > fix the driver so it does not do the deallocation/allocation needlessly.
 > Here's the next patch for the first target...
 > 
 > Index: uvm_map.c
 > ===================================================================
 > RCS file: /cvsroot/src/sys/uvm/uvm_map.c,v
 > retrieving revision 1.332
 > diff -u -u -r1.332 uvm_map.c
 > --- uvm_map.c	23 Jan 2015 16:13:53 -0000	1.332
 > +++ uvm_map.c	1 Feb 2015 16:29:46 -0000
 > @@ -1182,8 +1182,10 @@
 >  	 * If the kernel pmap can't map the requested space,
 >  	 * then allocate more resources for it.
 >  	 */
 > -	if (map == kernel_map && uvm_maxkaddr < (start + size))
 > -		uvm_maxkaddr = pmap_growkernel(start + size);
 > +	if (map == kernel_map && uvm_maxkaddr < (start + size)) {
 > +		if (flags & UVM_FLAG_NOWAIT == 0)
 > +			uvm_maxkaddr = pmap_growkernel(start + size);
 > +	}
 >  #endif
 >  
 >  	UVMMAP_EVCNT_INCR(map_call);
 
 
 that is not legal.  pmap_growkernel() is not optional for kmem allocations
 which increase the maximum kmem address in use.
 
 and before you try to dive in and make a nowait version of pmap_growkernel(),
 let's discuss if that's the way we want to resolve this.  it's currently
 illegal to allocate kernel memory (even with nowait/nosleep) while holding a
 spin mutex.  if we want to keep that restriction, then we just need to change
 this one driver to not do that.  if we want to relax that restriction,
 there a bunch of UVM and pmap changes needed.
 
 -Chuck