Commit fcc16882 authored Dec 19, 2012 by Stephen Boyd Committed by Linus Torvalds Dec 20, 2012

lib: atomic64: Initialize locks statically to fix early users



The atomic64 library uses a handful of static spin locks to implement
atomic 64-bit operations on architectures without support for atomic
64-bit instructions.

Unfortunately, the spinlocks are initialized in a pure initcall and that
is too late for the vfs namespace code which wants to use atomic64
operations before the initcall is run.

This became a problem as of commit 8823c079: "vfs: Add setns support
for the mount namespace".

This leads to BUG messages such as:

  BUG: spinlock bad magic on CPU#0, swapper/0/0
   lock: atomic64_lock+0x240/0x400, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
    do_raw_spin_lock+0x158/0x198
    _raw_spin_lock_irqsave+0x4c/0x58
    atomic64_add_return+0x30/0x5c
    alloc_mnt_ns.clone.14+0x44/0xac
    create_mnt_ns+0xc/0x54
    mnt_init+0x120/0x1d4
    vfs_caches_init+0xe0/0x10c
    start_kernel+0x29c/0x300

coming out early on during boot when spinlock debugging is enabled.

Fix this by initializing the spinlocks statically at compile time.

Reported-and-tested-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 787314c3

lib/atomic64.c

+5 −12

Original line number	Diff line number	Diff line
		@@ -31,7 +31,11 @@
		static union {
		raw_spinlock_t lock;
		char pad[L1_CACHE_BYTES];
		} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp;
		} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
		[0 ... (NR_LOCKS - 1)] = {
		.lock = __RAW_SPIN_LOCK_UNLOCKED(atomic64_lock.lock),
		},
		};

		static inline raw_spinlock_t lock_addr(const atomic64_t v)
		{
		@@ -173,14 +177,3 @@ int atomic64_add_unless(atomic64_t *v, long long a, long long u)
		return ret;
		}
		EXPORT_SYMBOL(atomic64_add_unless);

		static int init_atomic64_lock(void)
		{
		int i;

		for (i = 0; i < NR_LOCKS; ++i)
		raw_spin_lock_init(&atomic64_lock[i].lock);
		return 0;
		}

		pure_initcall(init_atomic64_lock);

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