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authorRoland McGrath <roland@gnu.org>1996-01-04 00:06:01 +0000
committerRoland McGrath <roland@gnu.org>1996-01-04 00:06:01 +0000
commit6df1b2474adfc23c9cfff5a4496108bea0c37511 (patch)
tree48bd35ba5b0d766560edde694efec2b791ada613 /sysdeps/mach/hurd/fork.c
parent71733723fb421bd54467d1a27096463ed1dcc2ed (diff)
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Rewritten.cvs/libc-960103
Diffstat (limited to 'sysdeps/mach/hurd/fork.c')
-rw-r--r--sysdeps/mach/hurd/fork.c22
1 files changed, 20 insertions, 2 deletions
diff --git a/sysdeps/mach/hurd/fork.c b/sysdeps/mach/hurd/fork.c
index 25279645ee..6fadb3d97d 100644
--- a/sysdeps/mach/hurd/fork.c
+++ b/sysdeps/mach/hurd/fork.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1994, 1995 Free Software Foundation, Inc.
+/* Copyright (C) 1994, 1995, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -121,7 +121,6 @@ __fork (void)
__spin_lock (&_hurd_ports[i].lock);
ports_locked = 1;
- *(volatile task_t *) &__mach_task_self_; /* XXX work around kernel bug */
/* Stop all other threads while copying the address space,
so nothing changes. */
@@ -130,6 +129,25 @@ __fork (void)
{
stopped = 1;
+#define XXX_KERNEL_PAGE_FAULT_BUG /* XXX work around page fault bug in mk */
+
+#ifdef XXX_KERNEL_PAGE_FAULT_BUG
+ /* Gag me with a pitchfork.
+ The bug scenario is this:
+
+ - The page containing __mach_task_self_ is paged out.
+ - The signal thread was faulting on that page when we
+ suspended it via proc_dostop. It holds some lock, or set
+ some busy bit, or somesuch.
+ - Now this thread faults on that same page.
+ - GRATUIOUS DEADLOCK
+
+ We can break the deadlock by aborting the thread that faulted
+ first, which if the bug happened was the signal thread because
+ it is the only other thread and we just suspended it.
+ */
+ __thread_abort (_hurd_msgport_thread);
+#endif
/* Create the child task. It will inherit a copy of our memory. */
err = __task_create (__mach_task_self (), 1, &newtask);
}