PATCH 2.4.18-rc2-ac1: hang on spinlock in "expand_stack"

From: Kevin Buhr (buhr@telus.net)
Date: Sat Mar 02 2002 - 21:36:12 EST


Alan:

I've enclosed a patch against 2.4.18-rc2-ac1, but it appears the same
bug still exists in 2.4.19-pre1-ac1. The "ac"-branch version of
"expand_stack" in "mm/mmap.c" has a code path that doesn't unlock the
spinlock. I noticed when a "gdb" bug tickled it and locked up my
machine.

Kevin Buhr <buhr@telus.net>

                        * * *

--- linux-2.4.18-rc2-ac1/mm/mmap.c Tue Feb 19 19:13:57 2002
+++ linux-2.4.18-rc2-ac1-local/mm/mmap.c Sat Mar 2 17:58:47 2002
@@ -762,8 +762,10 @@
         grow = (vma->vm_start - address) >> PAGE_SHIFT;
 
         /* Overcommit.. */
- if(!vm_enough_memory(grow, 1))
+ if(!vm_enough_memory(grow, 1)) {
+ spin_unlock(&vma->vm_mm->page_table_lock);
                 return -ENOMEM;
+ }
         
         if (vma->vm_end - address > current->rlim[RLIMIT_STACK].rlim_cur ||
             ((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->rlim[RLIMIT_AS].rlim_cur) {
-
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