2008-02-08 Neal H. Walfield <neal@gnu.org>

	* pager.c (__attribute__): New function.
	(pager_fault): Call it before taking PAGERS_LOCK.

1 files changed, 14 insertions, 0 deletions

diff --git a/libhurd-mm/pager.c b/libhurd-mm/pager.c
index 4823c23..558dccc 100644
--- a/libhurd-mm/pager.c
+++ b/libhurd-mm/pager.c
@@ -90,6 +90,18 @@ pager_deinstall (struct pager *pager)
   hurd_btree_pager_detach (&pagers, pager);
 }
 
+static void __attribute__ ((noinline))
+ensure_stack(int i)
+{
+  /* XXX: If we fault on the stack while we have PAGERS_LOCK, we
+     deadlock.  Ensure that we have some stack space and hope it is
+     enough.  (This can't be too much as we may be running on the
+     exception handler's stack.)  */
+  volatile char space[1024 + 512];
+  space[0] = 0;
+  space[sizeof (space) - 1] = 0;
+}
+
 bool
 pager_fault (addr_t addr, uintptr_t ip, struct exception_info info)
 {
@@ -98,6 +110,8 @@ pager_fault (addr_t addr, uintptr_t ip, struct exception_info info)
   region.start = addr;
   region.count = 1;
 
+  ensure_stack (1);
+
   ss_mutex_lock (&pagers_lock);
 
   struct pager *pager = hurd_btree_pager_find (&pagers, &region);