linux-toradex.git/include/linux/spinlock_up.h, branch v4.11-rc3

locking/spinlock, arch: Update and fix spin_unlock_wait() implementations

2016-06-14T09:55:15+00:00

This patch updates/fixes all spin_unlock_wait() implementations.

The update is in semantics; where it previously was only a control
dependency, we now upgrade to a full load-acquire to match the
store-release from the spin_unlock() we waited on. This ensures that
when spin_unlock_wait() returns, we're guaranteed to observe the full
critical section we waited on.

This fixes a number of spin_unlock_wait() users that (not
unreasonably) rely on this.

I also fixed a number of ticket lock versions to only wait on the
current lock holder, instead of for a full unlock, as this is
sufficient.

Furthermore; again for ticket locks; I added an smp_rmb() in between
the initial ticket load and the spin loop testing the current value
because I could not convince myself the address dependency is
sufficient, esp. if the loads are of different sizes.

I'm more than happy to remove this smp_rmb() again if people are
certain the address dependency does indeed work as expected.

Note: PPC32 will be fixed independently

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: chris@zankel.net
Cc: cmetcalf@mellanox.com
Cc: davem@davemloft.net
Cc: dhowells@redhat.com
Cc: james.hogan@imgtec.com
Cc: jejb@parisc-linux.org
Cc: linux@armlinux.org.uk
Cc: mpe@ellerman.id.au
Cc: ralf@linux-mips.org
Cc: realmz6@gmail.com
Cc: rkuo@codeaurora.org
Cc: rth@twiddle.net
Cc: schwidefsky@de.ibm.com
Cc: tony.luck@intel.com
Cc: vgupta@synopsys.com
Cc: ysato@users.sourceforge.jp
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

sched: Rename sched.c as sched/core.c in comments and Documentation

2013-06-19T10:58:42+00:00

Most of the stuff from kernel/sched.c was moved to kernel/sched/core.c long time
back and the comments/Documentation never got updated.

I figured it out when I was going through sched-domains.txt and so thought of
fixing it globally.

I haven't crossed check if the stuff that is referenced in sched/core.c by all
these files is still present and hasn't changed as that wasn't the motive behind
this patch.

Signed-off-by: Viresh Kumar 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/cdff76a265326ab8d71922a1db5be599f20aad45.1370329560.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar

spinlocks and preemption points need to be at least compiler barriers

2013-04-09T17:48:33+00:00

In UP and non-preempt respectively, the spinlocks and preemption
disable/enable points are stubbed out entirely, because there is no
regular code that can ever hit the kind of concurrency they are meant to
protect against.

However, while there is no regular code that can cause scheduling, we
_do_ end up having some exceptional (literally!) code that can do so,
and that we need to make sure does not ever get moved into the critical
region by the compiler.

In particular, get_user() and put_user() is generally implemented as
inline asm statements (even if the inline asm may then make a call
instruction to call out-of-line), and can obviously cause a page fault
and IO as a result.  If that inline asm has been scheduled into the
middle of a preemption-safe (or spinlock-protected) code region, we
obviously lose.

Now, admittedly this is *very* unlikely to actually ever happen, and
we've not seen examples of actual bugs related to this.  But partly
exactly because it's so hard to trigger and the resulting bug is so
subtle, we should be extra careful to get this right.

So make sure that even when preemption is disabled, and we don't have to
generate any actual *code* to explicitly tell the system that we are in
a preemption-disabled region, we need to at least tell the compiler not
to move things around the critical region.

This patch grew out of the same discussion that caused commits
79e5f05edcbf ("ARC: Add implicit compiler barrier to raw_local_irq*
functions") and 3e2e0d2c222b ("tile: comment assumption about
__insn_mtspr for ") to come about.

Note for stable: use discretion when/if applying this.  As mentioned,
this bug may never have actually bitten anybody, and gcc may never have
done the required code motion for it to possibly ever trigger in
practice.

Cc: stable@vger.kernel.org
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Signed-off-by: Linus Torvalds

spinlock_up.h: include asm/processor.h in for cpu_relax

2011-05-20T19:51:07+00:00

Commit e66eed651fd1 ("list: remove prefetching from regular list
iterators") removed the include of prefetch.h from list.h and this was a
path to including asm/processor.h.  We need to include it excplicitly
now.

Fixes this build error on sparc32 (at least):

  In file included from include/linux/seqlock.h:29,
                   from include/linux/time.h:8,
                   from include/linux/timex.h:56,
                   from include/linux/sched.h:57,
                   from arch/sparc/kernel/asm-offsets.c:13:
  include/linux/spinlock.h: In function 'spin_unlock_wait':
  include/linux/spinlock.h:360: error: implicit declaration of function 'cpu_relax

Signed-off-by: Stephen Rothwell 
Signed-off-by: Linus Torvalds

locking: Convert raw_rwlock functions to arch_rwlock

2009-12-14T22:55:32+00:00

Name space cleanup for rwlock functions. No functional change.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra 
Acked-by: David S. Miller 
Acked-by: Ingo Molnar 
Cc: linux-arch@vger.kernel.org

locking: Convert __raw_spin* functions to arch_spin*

2009-12-14T22:55:32+00:00

Name space cleanup. No functional change.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra 
Acked-by: David S. Miller 
Acked-by: Ingo Molnar 
Cc: linux-arch@vger.kernel.org

locking: Convert raw_spinlock to arch_spinlock

2009-12-14T22:55:32+00:00

The raw_spin* namespace was taken by lockdep for the architecture
specific implementations. raw_spin_* would be the ideal name space for
the spinlocks which are not converted to sleeping locks in preempt-rt.

Linus suggested to convert the raw_ to arch_ locks and cleanup the
name space instead of using an artifical name like core_spin,
atomic_spin or whatever

No functional change.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra 
Acked-by: David S. Miller 
Acked-by: Ingo Molnar 
Cc: linux-arch@vger.kernel.org

spinlock: Add missing __raw_spin_lock_flags() stub for UP

2009-06-10T09:48:14+00:00

This was only defined with CONFIG_DEBUG_SPINLOCK set, but some
obscure arch/powerpc code wants it always.

Signed-off-by: Benjamin Herrenschmidt 
Acked-by: Peter Zijlstra 
LKML-Reference: 
Signed-off-by: Ingo Molnar

spinlock: lockbreak cleanup

2008-01-30T12:31:20+00:00

The break_lock data structure and code for spinlocks is quite nasty.
Not only does it double the size of a spinlock but it changes locking to
a potentially less optimal trylock.

Put all of that under CONFIG_GENERIC_LOCKBREAK, and introduce a
__raw_spin_is_contended that uses the lock data itself to determine whether
there are waiters on the lock, to be used if CONFIG_GENERIC_LOCKBREAK is
not set.

Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to
decouple it from the spinlock implementation, and make it typesafe (rwlocks
do not have any need_lockbreak sites -- why do they even get bloated up
with that break_lock then?).

Signed-off-by: Nick Piggin 
Signed-off-by: Ingo Molnar 
Signed-off-by: Thomas Gleixner

[PATCH] lockdep: prove spinlock rwlock locking correctness

2006-07-03T22:27:04+00:00

Use the lock validator framework to prove spinlock and rwlock locking
correctness.

Signed-off-by: Ingo Molnar 
Signed-off-by: Arjan van de Ven 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds