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  1. 13 Jan, 2005 9 commits
    • Andrew Morton's avatar
      [SPARC64]: Make first arg to find_next_zero_bit() const. · 97edbb7f
      Andrew Morton authored 
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      97edbb7f
    • David S. Miller's avatar
      Merge nuts.davemloft.net:/disk1/BK/sparcwork-2.6 · de44a4dd
      David S. Miller authored 
      into nuts.davemloft.net:/disk1/BK/sparc-2.6
      de44a4dd
    • Paul Mackerras's avatar
      [PATCH] PPC64 Move thread_info flags to its own cache line · de10f9d4
      Paul Mackerras authored 
      This patch fixes a problem I have been seeing since all the preempt
changes went in, which is that ppc64 SMP systems would livelock
randomly if preempt was enabled.

It turns out that what was happening was that one cpu was spinning in
spin_lock_irq (the version at line 215 of kernel/spinlock.c) madly
doing preempt_enable() and preempt_disable() calls.  The other cpu had
the lock and was trying to set the TIF_NEED_RESCHED flag for the task
running on the first cpu.  That is an atomic operation which has to be
retried if another cpu writes to the same cacheline between the load
and the store, which the other cpu was doing every time it did
preempt_enable() or preempt_disable().

I decided to move the thread_info flags field into the next cache
line, since it is the only field that would regularly be modified by
cpus other than the one running the task that owns the thread_info.
(OK possibly the `cpu' field would be on a rebalance; I don't know the
rebalancing code, but that should be pretty infrequent.)  Thus, moving
the flags field seems like a good idea generally as well as solving the
immediate problem.

For the record I am pretty unhappy with the code we use for spin_lock
et al. with preemption turned on (the BUILD_LOCK_OPS stuff in
spinlock.c).  For a start we do the atomic op (_raw_spin_trylock) each
time around the loop.  That is going to be generating a lot of
unnecessary bus (or fabric) traffic.  Instead, after we fail to get
the lock we should poll it with simple loads until we see that it is
clear and then retry the atomic op.  Assuming a reasonable cache
design, the loads won't generate any bus traffic until another cpu
writes to the cacheline containing the lock.

Secondly we have lost the __spin_yield call that we had on ppc64,
which is an important optimization when we are running under the
hypervisor.  I can't just put that in cpu_relax because I need to know
which (virtual) cpu is holding the lock, so that I can tell the
hypervisor which virtual cpu to give my time slice to.  That
information is stored in the lock variable, which is why __spin_yield
needs the address of the lock.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      de10f9d4
    • Paul Mackerras's avatar
      [PATCH] PPC64 Add PREEMPT_BKL option · c08c4dd5
      Paul Mackerras authored 
      This patch adds the PREEMPT_BKL config option for PPC64, shamelessly
stolen from the i386 version.  I have this turned on in the kernel on
my desktop G5 and it seems to be just fine.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      c08c4dd5
    • Paul Mackerras's avatar
      [PATCH] PPC64 can do preempt debug too · 44462c19
      Paul Mackerras authored 
      This patch enables the DEBUG_PREEMPT config option for PPC64.  I have
this turned on on my desktop G5 and it isn't finding any problems.
(It did find one problem, in flush_tlb_pending(), that I have just
sent a patch for.)

BTW, do we really need to restrict which architectures the config
option is available on?
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      44462c19
    • Paul Mackerras's avatar
      [PATCH] PPC64 Call preempt_schedule on exception exit · f4d0d3c5
      Paul Mackerras authored 
      This patch mirrors the recent changes on x86 to call preempt_schedule
rather than schedule in the exception exit path, in the case where the
preempt_count is zero and the TIF_NEED_RESCHED bit is set.

I'm a little concerned that this means that we have a window where
interrupts are enabled and we are on our way into preempt_schedule,
but preempt_count is still zero.  Ingo's proposed preempt_schedule_irq
would fix this, and I think something like that should go in.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      f4d0d3c5
    • Paul Mackerras's avatar
      [PATCH] PPC64 Disable preemption in flush_tlb_pending · ec72859c
      Paul Mackerras authored 
      The preempt debug stuff found a place where we were using
smp_processor_id() without having preemption disabled, in
flush_tlb_pending.  This patch fixes it by using get_cpu_var and
put_cpu_var instead of the __get_cpu_var variant.
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      ec72859c
    • Jens Axboe's avatar
      [PATCH] possible rq starvation on oom · 80ce63d3
      Jens Axboe authored 
      I stumbled across this the other day. The block layer only uses a single
memory pool for request allocation, so it's very possible for eg writes
to have allocated them all at any point in time. If that is the case and
the machine is low on memory, a reader attempting to allocate a request
and failing in blk_alloc_request() can get stuck for a long time since
no one is there to wake it up.

The solution is either to add the extra mempool so both reads and writes
have one, or attempt to handle the situation. I chose the latter, to
save the extra memory required for the additional mempool with
BLKDEV_MIN_RQ statically allocated requests per-queue.

If a read allocation fails and we have no readers in flight for this
queue, mark us rq-starved so that the next write being freed will wake
up the sleeping reader(s). Same situation would happen for writes as
well of course, it's just a lot more unlikely.
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      80ce63d3
    • Jens Axboe's avatar
      [PATCH] Don't enable ata over eth by default · 6ddb58de
      Jens Axboe authored 
      "ATA over Ethernet support" should not default to 'm', it doesn't make
any sense for a special case driver to do so.
Signed-off-by: default avatarJens Axboe <axboe@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      6ddb58de
  3. 12 Jan, 2005 31 commits
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