This fixes a bug which was introduced when the code was switched to use
atomic_read()s.

The bug prevents hot-unplugging of SCSI (or emulated SCSI) devices from
working. 

From Patrick Mansfield.

They can happen on x86 as a result of interrupts in BIOS calls.

Noted by Manfred Spraul.

into home.osdl.org:/home/torvalds/v2.5/linux

into home.osdl.org:/home/torvalds/v2.5/linux

into samba.org:/stuff/paulus/kernel/for-linus-ppc

into home.osdl.org:/home/torvalds/v2.5/linux

into home.osdl.org:/home/torvalds/v2.5/linux

jiffies based values to ms. This fix crazy key repeat on ADB
based PowerMacs

use a NULL "driver" pointer and actually try to call it after
casting it !

properly with HZ != 100, causing tb_to_us to be wrong and gettimeofday()
to return strangely "off" results

core99 dual G4s).

registers exist on common CPUs and without those definitions, SMP won't
build

without this, you get no display on machines with those cards

so that the kernel boots at least on POWER4 and G5 CPUs

(missing from a previous cset)

of "standard" configs on oldworld macs

the coff image to randomly fail

 - Implement write-buffer flushing by garbage collection instead of padding.
 - Implement selective write-buffer flushing on fsync(). 
 - Implement error recovery on write-buffer flush.
 - Fix remove_suid(). Writing to a suid file didn't previously mark the file non-suid.
 - Fix handling of full file systems, to avoid unlink() returning -ENOSPC.
 - Fix assorted memory leaks.
 - Improve garbage collection efficiency by merging fewer pages.

into home.osdl.org:/home/torvalds/v2.5/linux

into home.osdl.org:/home/torvalds/v2.5/linux

into home.osdl.org:/home/torvalds/v2.5/linux

There is a bug in cpufreq call back funtion in timer_tsc routines,
that can result in system deadlock. The issue is: grabbing the
write_lock on xtime_lock without disabling the interrupts. So,=20
if we happen to get a timer interrupt while we are in this code,
system will go into a deadlock.

This bug only effects the kernels that have CONFIG_CPU_FREQ enabled.

into kernel.crashing.org:/home/benh/kernels/for-linus-ppc

This fixes two del_timer_sync() races that are still in the timer code. 

The first race was actually triggered in a 2.4 backport of the 2.6 timer
code.  The second race was never triggered - it is mostly theoretical on
a standalone kernel.  (It's more likely in any virtualized or otherwise
preemptable environment.)

Both races happen when self-rearming timers are used.  One mainstream
example is kernel/itimer.c.  The effect of the races is that
del_timer_sync() lets a timer running instead of synchronizing with it,
causing logic bugs (and crashes) in the affected kernel code.  One
typical incarnation of the race is a double add_timer(). 

race #1:

this code in __run_timers() is running on CPU0:

                        list_del(&timer->entry);
                        timer->base = NULL;
			[*]
                        set_running_timer(base, timer);
                        spin_unlock_irq(&base->lock);
			[**]
                        fn(data);
                        spin_lock_irq(&base->lock);

CPU0 gets stuck at the [*] code-point briefly - after the timer->base has
been set to NULL, but before the base->running_timer pointer has been set
up. This is a fundamentally volatile scenario, as there's _zero_ knowledge
in the data structures that this timer is about to be executed!

Now CPU1 comes along and calls del_timer_sync(). It will find nothing -
neither timer->base nor base->running_timer will cause it to synchronize.  
It will return and report that the timer has been deleted - shortly
afterwards CPU1 continues to execute the timer fn, which will cause
crashes.

This particular race is easy to fix by reordering the timer->base
clearing with set_running_timer(), and putting a wmb() between them, but
there's more races:

race #2

The checking of del_timer_sync() for 'pending or running timer' is
fundamentally unrobust. Eg. if CPU0 gets stuck at the [***] point below:

                base = &per_cpu(tvec_bases, i);
                if (base->running_timer == timer) {
                        while (base->running_timer == timer) {
                                cpu_relax();
                                preempt_check_resched();
                        }
			[***]
                        break;
                }
        }
        smp_rmb();
        if (timer_pending(timer))
                goto del_again;


then del_timer_sync() has already decided that this timer is not running
(we just finished loop-waiting for it), but we have not done the
timer_pending() check yet.

If the timer has re-armed itself, and if the timer expires on CPU1 (this
needs a long delay on CPU0 but that's not hard to achieve eg.  in UML or
with kernel preemption enabled), then CPU1 could start to expire the
timer and gets to the [**] point in __run_timers (see above), then CPU1
gets stalled and CPU0 is unstalled, then the timer_pending() check in
del_timer_sync() will not notice the running timer, and del_timer_sync()
returns - while CPU1 is just about to run the timer!

Fixing this second race is hard - it involves a heavy race-check
operation that has to lock all bases, and has to re-check the
base->running_timer value, and timer_pending condition atomically.

This fix also fixes the first race, due to forcing del_timer_sync() to
always observe the timer state atomically, so the [*] code point will
always synchronize with del_timer_sync(). 

The patch is ugly but safe, and it has fixed the crashes in the 2.4
backport.  I tested the patch on 2.6.0-test7 with some heavy itimer use
and it works fine.  Removing self-arming timers safely is the sole
purpose of del_timer_sync(), so there's no way around this overhead i
think.  I believe we should ultimately fix all major del_timer_sync()
users to not use self-arming timers - having del_timer_sync() in the
thread-exit path is now a considerable source of SMP overhead.  But this
is out of the scope of current 2.6 fixes of course, and we have to
support self-arming timers as well.

into nuts.ninka.net:/disk1/davem/BK/sparc-2.5

into kernel.crashing.org:/home/benh/kernels/for-linus-ppc

Now that it works, we can enable sn2 in generic builds.  This should not
only allow generic kernels to work on sn2, but also fix the build
problems people have been seeing with the qla1280 driver.  I tested a
generic kernel built with this patch on zx1 and it worked.

This corrects the save/restore code in mca_asm.S
which was written long ago, before the assembler understood
mnemonic names for 'cr' and 'ar' registers (in fact it
appears to have been written pre-silicon, some of the
control register numbers don't match with what actually
got built).  There were other goofs too (like using
0, 1, 2, etc. for region register subscripts).

into home.osdl.org:/home/torvalds/v2.5/linux

into home.osdl.org:/home/torvalds/v2.5/linux

Now that the ACPI table parsing stuff has been fixed we can move
find_memory() back where it belongs--after the SRAT table has been
parsed.

This patch fixes the combination of CONFIG_DISCONTIGMEM and
CONFIG_VIRTUAL_MEM_MAP so that generic kernels will work on all ia64
platforms, including sn2, and also makes sn2 specific kernels work
(which I think is a first).

I've cleaned this patch up heavily based on feedback from yourself,
Christoph and others.  I've tested sn2, zx1, and dig (thanks Xavier!)
specific configurations, as well as a generic configuration that allows
the same binary to boot on zx1, dig, and sn2.