powerpc/kcsan: Properly instrument arch_spin_unlock()

The following boottime error is encountered with SMP kernel:

kcsan: improperly instrumented type=(0): arch_spin_unlock(&arch_spinlock)
kcsan: improperly instrumented type=(0): spin_unlock(&test_spinlock)
kcsan: improperly instrumented type=(KCSAN_ACCESS_WRITE): arch_spin_unlock(&arch_spinlock)
kcsan: improperly instrumented type=(KCSAN_ACCESS_WRITE): spin_unlock(&test_spinlock)
kcsan: improperly instrumented type=(KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND): arch_spin_unlock(&arch_spinlock)
kcsan: improperly instrumented type=(KCSAN_ACCESS_WRITE | KCSAN_ACCESS_COMPOUND): spin_unlock(&test_spinlock)
kcsan: selftest: test_barrier failed
kcsan: selftest: 2/3 tests passed
Kernel panic - not syncing: selftests failed

Properly instrument arch_spin_unlock() with kcsan_mb().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/57834a703dfa5d6c27c9de0a01329059636e5ab7.1685080579.git.christophe.leroy@csgroup.eu

powerpc: Fix eh field when calling lwarx on PPC32

Commit 9401f4e46cf6 ("powerpc: Use lwarx/ldarx directly instead of
PPC_LWARX/LDARX macros") properly handled the eh field of lwarx
in asm/bitops.h but failed to clear it for PPC32 in
asm/simple_spinlock.h

So, do as in arch_atomic_try_cmpxchg_lock(), set it to 1 if PPC64
but set it to 0 if PPC32. For that use IS_ENABLED(CONFIG_PPC64) which
returns 1 when CONFIG_PPC64 is set and 0 otherwise.

Fixes: 9401f4e46cf6 ("powerpc: Use lwarx/ldarx directly instead of PPC_LWARX/LDARX macros")
Cc: stable@vger.kernel.org # v5.15+
Reported-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
[mpe: Use symbolic names, use 'n' constraint per Segher]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a1176e19e627dd6a1b8d24c6c457a8ab874b7d12.1659430931.git.christophe.leroy@csgroup.eu

locking: Remove spin_lock_flags() etc

parisc, ia64 and powerpc32 are the only remaining architectures that
provide custom arch_{spin,read,write}_lock_flags() functions, which are
meant to re-enable interrupts while waiting for a spinlock.

However, none of these can actually run into this codepath, because
it is only called on architectures without CONFIG_GENERIC_LOCKBREAK,
or when CONFIG_DEBUG_LOCK_ALLOC is set without CONFIG_LOCKDEP, and none
of those combinations are possible on the three architectures.

Going back in the git history, it appears that arch/mn10300 may have
been able to run into this code path, but there is a good chance that
it never worked. On the architectures that still exist, it was
already impossible to hit back in 2008 after the introduction of
CONFIG_GENERIC_LOCKBREAK, and possibly earlier.

As this is all dead code, just remove it and the helper functions built
around it. For arch/ia64, the inline asm could be cleaned up, but
it seems safer to leave it untouched.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Link: https://lore.kernel.org/r/20211022120058.1031690-1-arnd@kernel.org

powerpc: Use lwarx/ldarx directly instead of PPC_LWARX/LDARX macros

Force the eh flag at 0 on PPC32.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1fc81f07cabebb875b963e295408cc3dd38c8d85.1614674882.git.christophe.leroy@csgroup.eu

powerpc/spinlock: Unserialize spin_is_locked

c6f5d02b6a0f (locking/spinlocks/arm64: Remove smp_mb() from
arch_spin_is_locked()) made it pretty official that the call
semantics do not imply any sort of barriers, and any user that
gets creative must explicitly do any serialization.

This creativity, however, is nowadays pretty limited:

1. spin_unlock_wait() has been removed from the kernel in favor
of a lock/unlock combo. Furthermore, queued spinlocks have now
for a number of years no longer relied on _Q_LOCKED_VAL for the
call, but any non-zero value to indicate a locked state. There
were cases where the delayed locked store could lead to breaking
mutual exclusion with crossed locking; such as with sysv ipc and
netfilter being the most extreme.

2. The auditing Andrea did in verified that remaining spin_is_locked()
no longer rely on such semantics. Most callers just use it to assert
a lock is taken, in a debug nature. The only user that gets cute is
NOLOCK qdisc, as of:

96009c7d500e (sched: replace __QDISC_STATE_RUNNING bit with a spin lock)

... which ironically went in the next day after c6f5d02b6a0f. This
change replaces test_bit() with spin_is_locked() to know whether
to take the busylock heuristic to reduce contention on the main
qdisc lock. So any races against spin_is_locked() for archs that
use LL/SC for spin_lock() will be benign and not break any mutual
exclusion; furthermore, both the seqlock and busylock have the same
scope.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210309015950.27688-3-dave@stgolabs.net

powerpc/spinlock: Define smp_mb__after_spinlock only once

Instead of both queued and simple spinlocks doing it. Move
it into the arch's spinlock.h.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210309015950.27688-2-dave@stgolabs.net

powerpc: remove unneeded semicolons

Remove superfluous semicolons after function definitions.

Signed-off-by: Chengyang Fan <cy.fan@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210125095338.1719405-1-cy.fan@huawei.com

powerpc: Move spinlock implementation to simple_spinlock

To prepare for queued spinlocks. This is a simple rename except to
update preprocessor guard name and a file reference.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200724131423.1362108-3-npiggin@gmail.com