Граф коммитов

8 Коммитов

Автор SHA1 Сообщение Дата
Chen Gang 26a247fd9f include/linux/list_bl.h: use bool instead of int for boolean functions
hlist_bl_unhashed() and hlist_bl_empty() are all boolean functions, so
return bool instead of int.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-17 15:09:34 -07:00
Paul E. McKenney 1658d35ead list: Use READ_ONCE() when testing for empty lists
Most of the list-empty-check macros (list_empty(), hlist_empty(),
hlist_bl_empty(), hlist_nulls_empty(), and hlist_nulls_empty()) use
an unadorned load to check the list header.  Given that these macros
are sometimes invoked without the protection of a lock, this is
not sufficient.  This commit therefore adds READ_ONCE() calls to
them.  This commit does not touch llist_empty() because it already
has the needed ACCESS_ONCE().

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-11-23 10:37:35 -08:00
Paul E. McKenney 7f5f873c6a rculist: Use WRITE_ONCE() when deleting from reader-visible list
The various RCU list-deletion macros (list_del_rcu(),
hlist_del_init_rcu(), hlist_del_rcu(), hlist_bl_del_init_rcu(),
hlist_bl_del_rcu(), hlist_nulls_del_init_rcu(), and hlist_nulls_del_rcu())
do plain stores into the ->next pointer of the preceding list elemment.
Unfortunately, the compiler is within its rights to (for example) use
byte-at-a-time writes to update the pointer, which would fatally confuse
concurrent readers.  This patch therefore adds the needed WRITE_ONCE()
macros.

KernelThreadSanitizer (KTSAN) reported the __hlist_del() issue, which
is a problem when __hlist_del() is invoked by hlist_del_rcu().

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-10-06 11:16:42 -07:00
Steven Whitehouse 49d0de082c rcu: Fix hlist_bl_set_first_rcu() annotation
Abhi noticed that we were getting a complaint from the RCU subsystem
about access of an RCU protected list under the write side bit lock.
This commit adds additional annotation to check both the RCU read
lock and the write side bit lock before printing a message.

Reported by: Abhijith Das <adas@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Tested-by: Abhijith Das <adas@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2013-03-12 14:07:41 -07:00
Christoph Hellwig 1879fd6a26 add hlist_bl_lock/unlock helpers
Now that the whole dcache_hash_bucket crap is gone, go all the way and
also remove the weird locking layering violations for locking the hash
buckets.  Add hlist_bl_lock/unlock helpers to move the locking into the
list abstraction instead of requiring each caller to open code it.
After all allowing for the bit locks is the whole point of these helpers
over the plain hlist variant.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-04-25 18:14:10 -07:00
Russell King 32385c7cf6 kernel: fix hlist_bl again
__d_rehash is dereferencing an almost-NULL pointer on my ARM926.
CONFIG_SMP=n and CONFIG_DEBUG_SPINLOCK=y.

The faulting instruction is:    strne   r3, [r2, #4]
and as can be seen from the register dump below, r2 is 0x00000001, hence
the faulting 0x00000005 address.

__d_rehash is essentially:

       spin_lock_bucket(b);
       entry->d_flags &= ~DCACHE_UNHASHED;
       hlist_bl_add_head_rcu(&entry->d_hash, &b->head);
       spin_unlock_bucket(b);

which is:

       bit_spin_lock(0, (unsigned long *)&b->head.first);
       entry->d_flags &= ~DCACHE_UNHASHED;
       hlist_bl_add_head_rcu(&entry->d_hash, &b->head);
       __bit_spin_unlock(0, (unsigned long *)&b->head.first);

bit_spin_lock(0, ptr) sets bit 0 of *ptr, in this case b->head.first if
CONFIG_SMP or CONFIG_DEBUG_SPINLOCK is set:

#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
       while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
               while (test_bit(bitnum, addr)) {
                       preempt_enable();
                       cpu_relax();
                       preempt_disable();
               }
       }
#endif

So, b->head.first starts off NULL, and becomes a non-NULL (address 1).
hlist_bl_add_head_rcu() does this:

static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
                                       struct hlist_bl_head *h)
{
       first = hlist_bl_first(h);
       n->next = first;
       if (first)
               first->pprev = &n->next;

It is the store to first->pprev which is faulting.

hlist_bl_first():

static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h)
{
       return (struct hlist_bl_node *)
               ((unsigned long)h->first & ~LIST_BL_LOCKMASK);
}

but:
#if defined(CONFIG_SMP)
#define LIST_BL_LOCKMASK        1UL
#else
#define LIST_BL_LOCKMASK        0UL
#endif

So, we have one piece of code which sets bit 0 of addresses, and another
bit of code which doesn't clear it before dereferencing the pointer if
!CONFIG_SMP && CONFIG_DEBUG_SPINLOCK.  With the patch below, I can again
sucessfully boot the kernel on my Versatile PB/926 platform.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-14 13:12:45 +00:00
Nick Piggin 2c6755988a fs: hlist UP debug fixup
Po-Yu Chuang <ratbert.chuang@gmail.com> noticed that hlist_bl_set_first could
crash on a UP system when LIST_BL_LOCKMASK is 0, because

	LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK));

always evaulates to true.

Fix the expression, and also avoid a dependency between bit spinlock
implementation and list bl code (list code shouldn't know anything
except that bit 0 is set when adding and removing elements). Eventually
if a good use case comes up, we might use this list to store 1 or more
arbitrary bits of data, so it really shouldn't be tied to locking either,
but for now they are helpful for debugging.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-14 02:36:43 +00:00
Nick Piggin 4e35e6070b kernel: add bl_list
Introduce a type of hlist that can support the use of the lowest bit in the
hlist_head. This will be subsequently used to implement per-bucket bit spinlock
for inode and dentry hashes, and may be useful in other cases such as network
hashes.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:31 +11:00