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Re: port-arm/38950 (shark, hpcarm kernels prone to hard hangs on process exit)
The following reply was made to PR port-arm/38950; it has been noted by GNATS.
From: Steve Woodford <scw%netbsd.org@localhost>
Subject: Re: port-arm/38950 (shark, hpcarm kernels prone to hard hangs on
Date: Mon, 23 Jun 2008 15:55:41 +0100
On Friday 20 June 2008 04:35:01 Rafal Boni wrote:
> This just occurred to me after having filed this in the "I don't
> have time to think about it right now" bin. The issue here is that
> the pmap code is using the last-active-lwp as a proxy for
> last-active-pmap. What we should do is just save the pmap pointed to
> by the last-active-lwp vs. the lwp itself.
While that may solve the problem, it may well work against the intention
of "last-active-pmap", which is to reduce the impact of
context-switching between user-mode processes/lwps.
A simple fix would be to add the following to pmap_deactivate():
RCS file: /cvsroot/src/sys/arch/arm/arm32/pmap.c,v
retrieving revision 1.177
diff -u -r1.177 pmap.c
--- pmap.c 17 Jun 2008 08:04:26 -0000 1.177
+++ pmap.c 23 Jun 2008 14:55:07 -0000
@@ -3882,6 +3882,14 @@
pmap_deactivate(struct lwp *l)
+ * If the process is exiting, make sure pmap_activate() does
+ * a full MMU context-switch and cache flush, which we might
+ * otherwise skip. See PR port-arm/38950.
+ if (l->l_proc->p_sflag & PS_WEXIT)
+ pmap_previous_active_lwp = NULL;
l->l_proc->p_vmspace->vm_map.pmap->pm_activated = false;
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