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Author SHA1 Message Date
Paul E. McKenney
d8fa25c4ef tools/memory-model: Add more LKMM limitations 
This commit adds more detail about compiler optimizations and
not-yet-modeled Linux-kernel APIs.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/20180926182920.27644-4-paulmck@linux.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-10-02 10:28:04 +02:00
SeongJae Park
3d2046a6fa tools/memory-model: Fix a README typo 
This commit fixes a duplicate-"the" typo in README.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/20180926182920.27644-3-paulmck@linux.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-10-02 10:28:03 +02:00
Alan Stern
6e89e831a9 tools/memory-model: Add extra ordering for locks and remove it for ordinary release/acquire 
More than one kernel developer has expressed the opinion that the LKMM
should enforce ordering of writes by locking.  In other words, given
the following code:

	WRITE_ONCE(x, 1);
	spin_unlock(&s):
	spin_lock(&s);
	WRITE_ONCE(y, 1);

the stores to x and y should be propagated in order to all other CPUs,
even though those other CPUs might not access the lock s.  In terms of
the memory model, this means expanding the cumul-fence relation.

Locks should also provide read-read (and read-write) ordering in a
similar way.  Given:

	READ_ONCE(x);
	spin_unlock(&s);
	spin_lock(&s);
	READ_ONCE(y);		// or WRITE_ONCE(y, 1);

the load of x should be executed before the load of (or store to) y.
The LKMM already provides this ordering, but it provides it even in
the case where the two accesses are separated by a release/acquire
pair of fences rather than unlock/lock.  This would prevent
architectures from using weakly ordered implementations of release and
acquire, which seems like an unnecessary restriction.  The patch
therefore removes the ordering requirement from the LKMM for that
case.

There are several arguments both for and against this change.  Let us
refer to these enhanced ordering properties by saying that the LKMM
would require locks to be RCtso (a bit of a misnomer, but analogous to
RCpc and RCsc) and it would require ordinary acquire/release only to
be RCpc.  (Note: In the following, the phrase "all supported
architectures" is meant not to include RISC-V.  Although RISC-V is
indeed supported by the kernel, the implementation is still somewhat
in a state of flux and therefore statements about it would be
premature.)

Pros:

	The kernel already provides RCtso ordering for locks on all
	supported architectures, even though this is not stated
	explicitly anywhere.  Therefore the LKMM should formalize it.

	In theory, guaranteeing RCtso ordering would reduce the need
	for additional barrier-like constructs meant to increase the
	ordering strength of locks.

	Will Deacon and Peter Zijlstra are strongly in favor of
	formalizing the RCtso requirement.  Linus Torvalds and Will
	would like to go even further, requiring locks to have RCsc
	behavior (ordering preceding writes against later reads), but
	they recognize that this would incur a noticeable performance
	degradation on the POWER architecture.  Linus also points out
	that people have made the mistake, in the past, of assuming
	that locking has stronger ordering properties than is
	currently guaranteed, and this change would reduce the
	likelihood of such mistakes.

	Not requiring ordinary acquire/release to be any stronger than
	RCpc may prove advantageous for future architectures, allowing
	them to implement smp_load_acquire() and smp_store_release()
	with more efficient machine instructions than would be
	possible if the operations had to be RCtso.  Will and Linus
	approve this rationale, hypothetical though it is at the
	moment (it may end up affecting the RISC-V implementation).
	The same argument may or may not apply to RMW-acquire/release;
	see also the second Con entry below.

	Linus feels that locks should be easy for people to use
	without worrying about memory consistency issues, since they
	are so pervasive in the kernel, whereas acquire/release is
	much more of an "experts only" tool.  Requiring locks to be
	RCtso is a step in this direction.

Cons:

	Andrea Parri and Luc Maranget think that locks should have the
	same ordering properties as ordinary acquire/release (indeed,
	Luc points out that the names "acquire" and "release" derive
	from the usage of locks).  Andrea points out that having
	different ordering properties for different forms of acquires
	and releases is not only unnecessary, it would also be
	confusing and unmaintainable.

	Locks are constructed from lower-level primitives, typically
	RMW-acquire (for locking) and ordinary release (for unlock).
	It is illogical to require stronger ordering properties from
	the high-level operations than from the low-level operations
	they comprise.  Thus, this change would make

		while (cmpxchg_acquire(&s, 0, 1) != 0)
			cpu_relax();

	an incorrect implementation of spin_lock(&s) as far as the
	LKMM is concerned.  In theory this weakness can be ameliorated
	by changing the LKMM even further, requiring
	RMW-acquire/release also to be RCtso (which it already is on
	all supported architectures).

	As far as I know, nobody has singled out any examples of code
	in the kernel that actually relies on locks being RCtso.
	(People mumble about RCU and the scheduler, but nobody has
	pointed to any actual code.  If there are any real cases,
	their number is likely quite small.)  If RCtso ordering is not
	needed, why require it?

	A handful of locking constructs (qspinlocks, qrwlocks, and
	mcs_spinlocks) are built on top of smp_cond_load_acquire()
	instead of an RMW-acquire instruction.  It currently provides
	only the ordinary acquire semantics, not the stronger ordering
	this patch would require of locks.  In theory this could be
	ameliorated by requiring smp_cond_load_acquire() in
	combination with ordinary release also to be RCtso (which is
	currently true on all supported architectures).

	On future weakly ordered architectures, people may be able to
	implement locks in a non-RCtso fashion with significant
	performance improvement.  Meeting the RCtso requirement would
	necessarily add run-time overhead.

Overall, the technical aspects of these arguments seem relatively
minor, and it appears mostly to boil down to a matter of opinion.
Since the opinions of senior kernel maintainers such as Linus,
Peter, and Will carry more weight than those of Luc and Andrea, this
patch changes the model in accordance with the maintainers' wishes.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180926182920.27644-2-paulmck@linux.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-10-02 10:28:01 +02:00
Paul E. McKenney
c4f790f244 tools/memory-model: Add litmus-test naming scheme 
This commit documents the scheme used to generate the names for the
litmus tests.

[ paulmck: Apply feedback from Andrea Parri and Will Deacon. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/20180926182920.27644-1-paulmck@linux.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-10-02 10:28:00 +02:00
Andrea Parri
71b7ff5ebc tools/memory-model: Rename litmus tests to comply to norm7 
norm7 produces the 'normalized' name of a litmus test,  when the test
can be generated from a single cycle that passes through each process
exactly once. The commit renames such tests in order to comply to the
naming scheme implemented by this tool.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180716180605.16115-14-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:30:36 +02:00
Yauheni Kaliuta
0fcff1715b tools/memory-model/Documentation: Fix typo, smb->smp 
The tools/memory-model/Documentation/explanation.txt file says
"For each other CPU C', smb_wmb() forces all po-earlier stores"
This commit therefore replaces the "smb_wmb()" with "smp_wmb()".

Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/20180716180605.16115-13-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:30:35 +02:00
Paul E. McKenney
24675bb554 tools/memory-model: Make scripts executable 
This commit makes the scripts executable to avoid the need for everyone
to do so manually in their archive.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/20180716180605.16115-7-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:30:17 +02:00
Mark Rutland
af41db5ef7 tools/memory-model: Remove ACCESS_ONCE() from model 
Since commit:

  b899a85043 ("compiler.h: Remove ACCESS_ONCE()")

... there has been no definition of ACCESS_ONCE() in the kernel tree,
and it has been necessary to use READ_ONCE() or WRITE_ONCE() instead.

Correspondingly, let's remove ACCESS_ONCE() from the kernel memory
model.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180716180605.16115-6-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:29:35 +02:00
Mark Rutland
5bde06b63a tools/memory-model: Remove ACCESS_ONCE() from recipes 
Since commit:

  b899a85043 ("compiler.h: Remove ACCESS_ONCE()")

... there has been no definition of ACCESS_ONCE() in the kernel tree,
and it has been necessary to use READ_ONCE() or WRITE_ONCE() instead.

Let's update the exmaples in recipes.txt likewise for consistency, using
READ_ONCE() for reads.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180716180605.16115-5-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:29:34 +02:00
Paul E. McKenney
acb6c96c52 tools/memory-model: Fix ISA2+pooncelock+pooncelock+pombonce name 
The names on the first line of the litmus tests are arbitrary,
but the convention is that they be the filename without the trailing
".litmus".  This commit therefore removes the stray trailing ".litmus"
from ISA2+pooncelock+pooncelock+pombonce.litmus's name.

Reported-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/20180716180605.16115-2-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:29:31 +02:00
Paul E. McKenney
b464818978 tools/memory-model: Add litmus test for full multicopy atomicity 
This commit adds a litmus test suggested by Alan Stern that is forbidden
on fully multicopy atomic systems, but allowed on other-multicopy and
on non-multicopy atomic systems.  For reference, s390 is fully multicopy
atomic, x86 and ARMv8 are other-multicopy atomic, and ARMv7 and powerpc
are non-multicopy atomic.

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/20180716180605.16115-1-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-07-17 09:29:29 +02:00
Andrea Parri
99c12749b1 tools/memory-model: Add reference for 'Simplifying ARM concurrency' 
The paper discusses the revised ARMv8 memory model; such revision
had an important impact on the design of the LKMM.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:19 +02:00
Andrea Parri
1a00b4554d tools/memory-model: Update ASPLOS information 
ASPLOS 2018 was held in March: make sure this is reflected in
header comments and references.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-18-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:18 +02:00
Andrea Parri
05604e7e3a tools/memory-model: Fix coding style in 'lock.cat' 
This commit uses tabs for indentation and adds spaces around binary
operator.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/1526340837-12222-16-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:18 +02:00
Alan Stern
cee0321a40 tools/memory-model: Remove out-of-date comments and code from lock.cat 
lock.cat contains old comments and code referring to the possibility
of LKR events that are not part of an RMW pair.  This is a holdover
from when I though we might end up using LKR events to implement
spin_is_locked().  Reword the comments to remove this assumption and
replace domain(lk-rmw) in the code with LKR.

Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
[ paulmck: Pulled as lock-nest into previous line as discussed. ]
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-15-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:18 +02:00
Alan Stern
30b795df11 tools/memory-model: Improve mixed-access checking in lock.cat 
The code in lock.cat which checks for normal read/write accesses to
spinlock variables doesn't take into account the newly added RL and RU
events.  Add them into the test, and move the resulting code up near
the start of the file, since a violation would indicate a pretty
severe conceptual error in a litmus test.

Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-14-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:18 +02:00
Alan Stern
fd0359dbac tools/memory-model: Improve comments in lock.cat 
This patch improves the comments in tools/memory-model/lock.cat.  In
addition to making the text more uniform and removing redundant
comments, it adds a description of all the possible locking events
that herd can generate.

Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-13-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:18 +02:00
Alan Stern
8559183cca tools/memory-model: Remove duplicated code from lock.cat 
This patch simplifies the implementation of spin_is_locked in the
LKMM.  It capitalizes on the fact that a failed spin_trylock() and a
spin_is_locked() which returns True have exactly the same semantics
(those of READ_ONCE) and ordering properties (none).  Therefore the
two kinds of events can be combined and handled by the same code,
instead of treated separately as they are currently.

Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-12-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:17 +02:00
Paul E. McKenney
1bd3742043 tools/memory-model: Flag "cumulativity" and "propagation" tests 
This commit flags WRC+pooncerelease+rmbonceonce+Once.litmus
as being forbidden by smp_store_release() A-cumulativity and
IRIW+mbonceonces+OnceOnce.litmus as being forbidden by the LKMM
propagation rule.

Suggested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
[ paulmck: Updated wording as suggested by Alan Stern. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-11-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:17 +02:00
Luc Maranget
15553dcbca tools/memory-model: Add model support for spin_is_locked() 
This commit first adds a trivial macro for spin_is_locked() to
linux-kernel.def.

It also adds cat code for enumerating all possible matches of lock
write events (set LKW) with islocked events returning true (set RL,
for Read from Lock), and unlock write events (set UL) with islocked
events returning false (set RU, for Read from Unlock).  Note that this
intentionally does not model uniprocessor kernels (CONFIG_SMP=n) built
with CONFIG_DEBUG_SPINLOCK=n, in which spin_is_locked() unconditionally
returns zero.

It also adds a pair of litmus tests demonstrating the minimal ordering
provided by spin_is_locked() in conjunction with spin_lock().  Will Deacon
noted that this minimal ordering happens on ARMv8:
https://lkml.kernel.org/r/20180226162426.GB17158@arm.com

Notice that herd7 installations strictly older than version 7.49
do not handle the new constructs.

Signed-off-by: Luc Maranget <luc.maranget@inria.fr>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <Luc.Maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/1526340837-12222-10-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:17 +02:00
Paul E. McKenney
2fb6ae162f tools/memory-model: Add scripts to test memory model 
This commit adds a pair of scripts that run the memory model on litmus
tests, checking that the verification result of each litmus test matches
the result flagged in the litmus test itself.  These scripts permit easier
checking of changes to the memory model against preconceived notions.

To run the scripts, go to the tools/memory-model directory and type
"scripts/checkalllitmus.sh".  If all is well, the last line printed will
be "All litmus tests verified as was expected."

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/1526340837-12222-9-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:17 +02:00
Andrea Parri
d17013e0ba tools/memory-model: Fix coding style in 'linux-kernel.def' 
This commit fixes white spaces around semicolons.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/1526340837-12222-8-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:17 +02:00
Andrea Parri
bf8c6d963d tools/memory-model: Model 'smp_store_mb()' 
This commit models 'smp_store_mb(x, val);' to be semantically equivalent
to 'WRITE_ONCE(x, val); smp_mb();'.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-7-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:16 +02:00
Paul E. McKenney
bfd403bb36 tools/memory-order: Update the cheat-sheet to show that smp_mb__after_atomic() orders later RMW operations 
The current cheat sheet does not claim that smp_mb__after_atomic()
orders later RMW atomic operations, which it must, at least against
earlier RMW atomic operations and whatever precedes them.

This commit therefore adds the needed "Y".

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-6-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:16 +02:00
Paul E. McKenney
35bb6ee679 tools/memory-order: Improve key for SELF and SV 
The key for "SELF" was missing completely and the key for "SV" was
a bit obtuse.  This commit therefore adds a key for "SELF" and improves
the one for "SV".

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/1526340837-12222-5-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 2018-05-15 08:11:16 +02:00