Merge git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial

S: Iasi 6600

S: Romania

N: Mark Adler

E: madler@alumni.caltech.edu

W: http://alumnus.caltech.edu/~madler/

D: zlib decompression

N: Monalisa Agrawal

E: magrawal@nortelnetworks.com

D: Basic Interphase 5575 driver with UBR and ABR support.

    <para>

      Our final dilemma is this: when can we actually destroy the

      removed element?  Remember, a reader might be stepping through

      this element in the list right now: it we free this element and

      this element in the list right now: if we free this element and

      the <symbol>next</symbol> pointer changes, the reader will jump

      off into garbage and crash.  We need to wait until we know that

      all the readers who were traversing the list when we deleted the

	smp_mb__before_atomic_dec();

	atomic_dec(&obj->ref_count);

It makes sure that all memory operations preceeding the atomic_dec()

It makes sure that all memory operations preceding the atomic_dec()

call are strongly ordered with respect to the atomic counter

operation.  In the above example, it guarentees that the assignment of

operation.  In the above example, it guarantees that the assignment of

"1" to obj->dead will be globally visible to other cpus before the

atomic counter decrement.

Without the explicitl smp_mb__before_atomic_dec() call, the

Without the explicit smp_mb__before_atomic_dec() call, the

implementation could legally allow the atomic counter update visible

to other cpus before the "obj->dead = 1;" assignment.

(smp_mb__{before,after}_atomic_inc()).

A missing memory barrier in the cases where they are required by the

atomic_t implementation above can have disasterous results.  Here is

an example, which follows a pattern occuring frequently in the Linux

atomic_t implementation above can have disastrous results.  Here is

an example, which follows a pattern occurring frequently in the Linux

kernel.  It is the use of atomic counters to implement reference

counting, and it works such that once the counter falls to zero it can

be guarenteed that no other entity can be accessing the object:

be guaranteed that no other entity can be accessing the object:

static void obj_list_add(struct obj *obj)

{

size.  The endianness of the bits within each "unsigned long" are the

native endianness of the cpu.

	void set_bit(unsigned long nr, volatils unsigned long *addr);

	void clear_bit(unsigned long nr, volatils unsigned long *addr);

	void change_bit(unsigned long nr, volatils unsigned long *addr);

	void set_bit(unsigned long nr, volatile unsigned long *addr);

	void clear_bit(unsigned long nr, volatile unsigned long *addr);

	void change_bit(unsigned long nr, volatile unsigned long *addr);

These routines set, clear, and change, respectively, the bit number

indicated by "nr" on the bit mask pointed to by "ADDR".

They must execute atomically, yet there are no implicit memory barrier

semantics required of these interfaces.

	int test_and_set_bit(unsigned long nr, volatils unsigned long *addr);

	int test_and_clear_bit(unsigned long nr, volatils unsigned long *addr);

	int test_and_change_bit(unsigned long nr, volatils unsigned long *addr);

	int test_and_set_bit(unsigned long nr, volatile unsigned long *addr);

	int test_and_clear_bit(unsigned long nr, volatile unsigned long *addr);

	int test_and_change_bit(unsigned long nr, volatile unsigned long *addr);

Like the above, except that these routines return a boolean which

indicates whether the changed bit was set _BEFORE_ the atomic bit

		/* ... */;

	obj->killed = 1;

The implementation of test_and_set_bit() must guarentee that

The implementation of test_and_set_bit() must guarantee that

"obj->dead = 1;" is visible to cpus before the atomic memory operation

done by test_and_set_bit() becomes visible.  Likewise, the atomic

memory operation done by test_and_set_bit() must become visible before

strictly orders all subsequent memory operations (including

the cas()) with respect to itself, things will be fine.

Said another way, _atomic_dec_and_lock() must guarentee that

Said another way, _atomic_dec_and_lock() must guarantee that

a counter dropping to zero is never made visible before the

spinlock being acquired.

(sometimes just a list) for the devices they control. There wasn't any

uniformity across the different bus types.

The current driver model provides a comon, uniform data model for describing

The current driver model provides a common, uniform data model for describing

a bus and the devices that can appear under the bus. The unified bus

model includes a set of common attributes which all busses carry, and a set

of common callbacks, such as device discovery during bus probing, bus

document trapinfo

	Run info threads and lookup pid of thread #1

	'trapinfo <pid>' will tell you by which trap & possibly

	addresthe kernel paniced.

	address the kernel panicked.

end