Rather than trying to wait until all possible lockers have
unlocked the lock, we now only wait until the current locker
(if any) has released the lock.

The old code was correct, but the new code works more like the x86
code and thus hopefully is more appropriate under contention.
See commit 78bff1c8 ("x86/ticketlock: Fix spin_unlock_wait()
livelock") for x86.
Signed-off-by: NChris Metcalf <cmetcalf@ezchip.com>

EXPORT_SYMBOL and inline directives are contradictory to each other.
The patch fixes this inconsistency.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: NDenis Efremov <yefremov.denis@gmail.com>
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

Parentheses were missing.
Signed-off-by: NRoel Kluin <roel.kluin@gmail.com>
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

The first issue fixed in this patch is that pending rwlock write locks
could lock out new readers; this could cause a deadlock if a read lock was
held on cpu 1, a write lock was then attempted on cpu 2 and was pending,
and cpu 1 was interrupted and attempted to re-acquire a read lock.
The write lock code was modified to not lock out new readers.

The second issue fixed is that there was a narrow race window where a tns
instruction had been issued (setting the lock value to "1") and the store
instruction to reset the lock value correctly had not yet been issued.
In this case, if an interrupt occurred and the same cpu then tried to
manipulate the lock, it would find the lock value set to "1" and spin
forever, assuming some other cpu was partway through updating it.  The fix
is to enforce an interrupt critical section around the tns/store pair.

In addition, this change now arranges to always validate that after
a readlock we have not wrapped around the count of readers, which
is only eight bits.

Since these changes make the rwlock "fast path" code heavier weight,
I decided to move all the rwlock code all out of line, leaving only the
conventional spinlock code with fastpath inlines.  Since the read_lock
and read_trylock implementations ended up very similar, I just expressed
read_lock in terms of read_trylock.

As part of this change I also eliminate support for the now-obsolete
tns_atomic mode.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

This avoids a deadlock in the IGMP code where one core gets a read
lock, another core starts trying to get a write lock (thus blocking
new readers), and then the first core tries to recursively re-acquire
the read lock.

We still try to preserve some degree of balance by giving priority
to additional write lockers that come along while the lock is held
for write, so they can all complete quickly and return the lock to
the readers.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

This change is the core kernel support for TILEPro and TILE64 chips.
No driver support (except the console driver) is included yet.

This includes the relevant Linux headers in asm/; the low-level
low-level "Tile architecture" headers in arch/, which are
shared with the hypervisor, etc., and are build-system agnostic;
and the relevant hypervisor headers in hv/.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reviewed-by: NPaul Mundt <lethal@linux-sh.org>