releases/3.4.25/lib-atomic64-initialize-locks-statically-to-fix-early-users.patch

   1 From fcc16882ac4532aaa644bff444f0c5d6228ba71e Mon Sep 17 00:00:00 2001
   2 From: Stephen Boyd <sboyd@codeaurora.org>
   3 Date: Wed, 19 Dec 2012 23:39:48 -0800
   4 Subject: lib: atomic64: Initialize locks statically to fix early users
   5
   6 From: Stephen Boyd <sboyd@codeaurora.org>
   7
   8 commit fcc16882ac4532aaa644bff444f0c5d6228ba71e upstream.
   9
  10 The atomic64 library uses a handful of static spin locks to implement
  11 atomic 64-bit operations on architectures without support for atomic
  12 64-bit instructions.
  13
  14 Unfortunately, the spinlocks are initialized in a pure initcall and that
  15 is too late for the vfs namespace code which wants to use atomic64
  16 operations before the initcall is run.
  17
  18 This became a problem as of commit 8823c079ba71: "vfs: Add setns support
  19 for the mount namespace".
  20
  21 This leads to BUG messages such as:
  22
  23   BUG: spinlock bad magic on CPU#0, swapper/0/0
  24    lock: atomic64_lock+0x240/0x400, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
  25     do_raw_spin_lock+0x158/0x198
  26     _raw_spin_lock_irqsave+0x4c/0x58
  27     atomic64_add_return+0x30/0x5c
  28     alloc_mnt_ns.clone.14+0x44/0xac
  29     create_mnt_ns+0xc/0x54
  30     mnt_init+0x120/0x1d4
  31     vfs_caches_init+0xe0/0x10c
  32     start_kernel+0x29c/0x300
  33
  34 coming out early on during boot when spinlock debugging is enabled.
  35
  36 Fix this by initializing the spinlocks statically at compile time.
  37
  38 Reported-and-tested-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
  39 Tested-by: Tony Lindgren <tony@atomide.com>
  40 Cc: Eric W. Biederman <ebiederm@xmission.com>
  41 Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
  42 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  43 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  44 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  45
  46 ---
  47  lib/atomic64.c |   17 +++++------------
  48  1 file changed, 5 insertions(+), 12 deletions(-)
  49
  50 --- a/lib/atomic64.c
  51 +++ b/lib/atomic64.c
  52 @@ -31,7 +31,11 @@
  53  static union {
  54         raw_spinlock_t lock;
  55         char pad[L1_CACHE_BYTES];
  56 -} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp;
  57 +} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
  58 +       [0 ... (NR_LOCKS - 1)] = {
  59 +               .lock =  __RAW_SPIN_LOCK_UNLOCKED(atomic64_lock.lock),
  60 +       },
  61 +};
  62
  63  static inline raw_spinlock_t *lock_addr(const atomic64_t *v)
  64  {
  65 @@ -173,14 +177,3 @@ int atomic64_add_unless(atomic64_t *v, l
  66         return ret;
  67  }
  68  EXPORT_SYMBOL(atomic64_add_unless);
  69 -
  70 -static int init_atomic64_lock(void)
  71 -{
  72 -       int i;
  73 -
  74 -       for (i = 0; i < NR_LOCKS; ++i)
  75 -               raw_spin_lock_init(&atomic64_lock[i].lock);
  76 -       return 0;
  77 -}
  78 -
  79 -pure_initcall(init_atomic64_lock);