[PATCHv2 4/4] tools/memory-model: Distinguish between syntactic and semantic tags

From: Jonas Oberhauser
Date: Tue Jun 04 2024 - 12:06:56 EST

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Not all tags that are always there syntactically also provide semantic
membership in the corresponding set. For example, an 'acquire tag on a
write does not imply that the write is finally in the Acquire set and
provides acquire ordering.

To distinguish in those cases between the syntactic tags and actual
sets, we capitalize the former, so 'ACQUIRE tags may be present on both
reads and writes, but only reads will appear in the Acquire set.

For tags where the two concepts are the same we do not use specific
capitalization to make this distinction.

Reported-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Jonas Oberhauser <jonas.oberhauser@xxxxxxxxxxxxxxx>
---
tools/memory-model/linux-kernel.bell | 22 ++--
tools/memory-model/linux-kernel.def | 176 +++++++++++++--------------
2 files changed, 99 insertions(+), 99 deletions(-)

diff --git a/tools/memory-model/linux-kernel.bell b/tools/memory-model/linux-kernel.bell
index 2f49993644ed..a27757470d29 100644
--- a/tools/memory-model/linux-kernel.bell
+++ b/tools/memory-model/linux-kernel.bell
@@ -13,18 +13,18 @@

"Linux-kernel memory consistency model"

-enum Accesses = 'once (*READ_ONCE,WRITE_ONCE*) ||
- 'release (*smp_store_release*) ||
- 'acquire (*smp_load_acquire*) ||
- 'noreturn (* R of non-return RMW *) ||
- 'mb (*xchg(),cmpxchg(),...*)
+enum Accesses = 'ONCE (*READ_ONCE,WRITE_ONCE*) ||
+ 'RELEASE (*smp_store_release*) ||
+ 'ACQUIRE (*smp_load_acquire*) ||
+ 'NORETURN (* R of non-return RMW *) ||
+ 'MB (*xchg(),cmpxchg(),...*)
instructions R[Accesses]
instructions W[Accesses]
instructions RMW[Accesses]

enum Barriers = 'wmb (*smp_wmb*) ||
'rmb (*smp_rmb*) ||
- 'mb (*smp_mb*) ||
+ 'MB (*smp_mb*) ||
'barrier (*barrier*) ||
'rcu-lock (*rcu_read_lock*) ||
'rcu-unlock (*rcu_read_unlock*) ||
@@ -38,10 +38,10 @@ instructions F[Barriers]

(* Remove impossible tags, such as Acquire on a store or failed RMW *)
let FailedRMW = RMW \ (domain(rmw) | range(rmw))
-let Acquire = Acquire \ W \ FailedRMW
-let Release = Release \ R \ FailedRMW
-let Mb = Mb \ FailedRMW
-let Noreturn = Noreturn \ W
+let Acquire = ACQUIRE \ W \ FailedRMW
+let Release = RELEASE \ R \ FailedRMW
+let Mb = MB \ FailedRMW
+let Noreturn = NORETURN \ W

(* SRCU *)
enum SRCU = 'srcu-lock || 'srcu-unlock || 'sync-srcu
@@ -81,7 +81,7 @@ flag ~empty rcu-rscs & (po ; [Sync-srcu] ; po) as invalid-sleep
flag ~empty different-values(srcu-rscs) as srcu-bad-value-match

(* Compute marked and plain memory accesses *)
-let Marked = (~M) | IW | Once | Release | Acquire | domain(rmw) | range(rmw) |
+let Marked = (~M) | IW | ONCE | RELEASE | ACQUIRE | MB | RMW |
LKR | LKW | UL | LF | RL | RU | Srcu-lock | Srcu-unlock
let Plain = M \ Marked

diff --git a/tools/memory-model/linux-kernel.def b/tools/memory-model/linux-kernel.def
index a12b96c547b7..001366ff3fb4 100644
--- a/tools/memory-model/linux-kernel.def
+++ b/tools/memory-model/linux-kernel.def
@@ -6,18 +6,18 @@
// which appeared in ASPLOS 2018.

// ONCE
-READ_ONCE(X) __load{once}(X)
-WRITE_ONCE(X,V) { __store{once}(X,V); }
+READ_ONCE(X) __load{ONCE}(X)
+WRITE_ONCE(X,V) { __store{ONCE}(X,V); }

// Release Acquire and friends
-smp_store_release(X,V) { __store{release}(*X,V); }
-smp_load_acquire(X) __load{acquire}(*X)
-rcu_assign_pointer(X,V) { __store{release}(X,V); }
-rcu_dereference(X) __load{once}(X)
-smp_store_mb(X,V) { __store{once}(X,V); __fence{mb}; }
+smp_store_release(X,V) { __store{RELEASE}(*X,V); }
+smp_load_acquire(X) __load{ACQUIRE}(*X)
+rcu_assign_pointer(X,V) { __store{RELEASE}(X,V); }
+rcu_dereference(X) __load{ONCE}(X)
+smp_store_mb(X,V) { __store{ONCE}(X,V); __fence{MB}; }

// Fences
-smp_mb() { __fence{mb}; }
+smp_mb() { __fence{MB}; }
smp_rmb() { __fence{rmb}; }
smp_wmb() { __fence{wmb}; }
smp_mb__before_atomic() { __fence{before-atomic}; }
@@ -28,14 +28,14 @@ smp_mb__after_srcu_read_unlock() { __fence{after-srcu-read-unlock}; }
barrier() { __fence{barrier}; }

// Exchange
-xchg(X,V) __xchg{mb}(X,V)
-xchg_relaxed(X,V) __xchg{once}(X,V)
-xchg_release(X,V) __xchg{release}(X,V)
-xchg_acquire(X,V) __xchg{acquire}(X,V)
-cmpxchg(X,V,W) __cmpxchg{mb}(X,V,W)
-cmpxchg_relaxed(X,V,W) __cmpxchg{once}(X,V,W)
-cmpxchg_acquire(X,V,W) __cmpxchg{acquire}(X,V,W)
-cmpxchg_release(X,V,W) __cmpxchg{release}(X,V,W)
+xchg(X,V) __xchg{MB}(X,V)
+xchg_relaxed(X,V) __xchg{ONCE}(X,V)
+xchg_release(X,V) __xchg{RELEASE}(X,V)
+xchg_acquire(X,V) __xchg{ACQUIRE}(X,V)
+cmpxchg(X,V,W) __cmpxchg{MB}(X,V,W)
+cmpxchg_relaxed(X,V,W) __cmpxchg{ONCE}(X,V,W)
+cmpxchg_acquire(X,V,W) __cmpxchg{ACQUIRE}(X,V,W)
+cmpxchg_release(X,V,W) __cmpxchg{RELEASE}(X,V,W)

// Spinlocks
spin_lock(X) { __lock(X); }
@@ -72,75 +72,75 @@ atomic_inc(X) { __atomic_op(X,+,1); }
atomic_dec(X) { __atomic_op(X,-,1); }
atomic_andnot(V,X) { __atomic_op(X,&~,V); }

-atomic_add_return(V,X) __atomic_op_return{mb}(X,+,V)
-atomic_add_return_relaxed(V,X) __atomic_op_return{once}(X,+,V)
-atomic_add_return_acquire(V,X) __atomic_op_return{acquire}(X,+,V)
-atomic_add_return_release(V,X) __atomic_op_return{release}(X,+,V)
-atomic_fetch_add(V,X) __atomic_fetch_op{mb}(X,+,V)
-atomic_fetch_add_relaxed(V,X) __atomic_fetch_op{once}(X,+,V)
-atomic_fetch_add_acquire(V,X) __atomic_fetch_op{acquire}(X,+,V)
-atomic_fetch_add_release(V,X) __atomic_fetch_op{release}(X,+,V)
-
-atomic_fetch_and(V,X) __atomic_fetch_op{mb}(X,&,V)
-atomic_fetch_and_relaxed(V,X) __atomic_fetch_op{once}(X,&,V)
-atomic_fetch_and_acquire(V,X) __atomic_fetch_op{acquire}(X,&,V)
-atomic_fetch_and_release(V,X) __atomic_fetch_op{release}(X,&,V)
-
-atomic_fetch_or(V,X) __atomic_fetch_op{mb}(X,|,V)
-atomic_fetch_or_relaxed(V,X) __atomic_fetch_op{once}(X,|,V)
-atomic_fetch_or_acquire(V,X) __atomic_fetch_op{acquire}(X,|,V)
-atomic_fetch_or_release(V,X) __atomic_fetch_op{release}(X,|,V)
-
-atomic_fetch_xor(V,X) __atomic_fetch_op{mb}(X,^,V)
-atomic_fetch_xor_relaxed(V,X) __atomic_fetch_op{once}(X,^,V)
-atomic_fetch_xor_acquire(V,X) __atomic_fetch_op{acquire}(X,^,V)
-atomic_fetch_xor_release(V,X) __atomic_fetch_op{release}(X,^,V)
-
-atomic_inc_return(X) __atomic_op_return{mb}(X,+,1)
-atomic_inc_return_relaxed(X) __atomic_op_return{once}(X,+,1)
-atomic_inc_return_acquire(X) __atomic_op_return{acquire}(X,+,1)
-atomic_inc_return_release(X) __atomic_op_return{release}(X,+,1)
-atomic_fetch_inc(X) __atomic_fetch_op{mb}(X,+,1)
-atomic_fetch_inc_relaxed(X) __atomic_fetch_op{once}(X,+,1)
-atomic_fetch_inc_acquire(X) __atomic_fetch_op{acquire}(X,+,1)
-atomic_fetch_inc_release(X) __atomic_fetch_op{release}(X,+,1)
-
-atomic_sub_return(V,X) __atomic_op_return{mb}(X,-,V)
-atomic_sub_return_relaxed(V,X) __atomic_op_return{once}(X,-,V)
-atomic_sub_return_acquire(V,X) __atomic_op_return{acquire}(X,-,V)
-atomic_sub_return_release(V,X) __atomic_op_return{release}(X,-,V)
-atomic_fetch_sub(V,X) __atomic_fetch_op{mb}(X,-,V)
-atomic_fetch_sub_relaxed(V,X) __atomic_fetch_op{once}(X,-,V)
-atomic_fetch_sub_acquire(V,X) __atomic_fetch_op{acquire}(X,-,V)
-atomic_fetch_sub_release(V,X) __atomic_fetch_op{release}(X,-,V)
-
-atomic_dec_return(X) __atomic_op_return{mb}(X,-,1)
-atomic_dec_return_relaxed(X) __atomic_op_return{once}(X,-,1)
-atomic_dec_return_acquire(X) __atomic_op_return{acquire}(X,-,1)
-atomic_dec_return_release(X) __atomic_op_return{release}(X,-,1)
-atomic_fetch_dec(X) __atomic_fetch_op{mb}(X,-,1)
-atomic_fetch_dec_relaxed(X) __atomic_fetch_op{once}(X,-,1)
-atomic_fetch_dec_acquire(X) __atomic_fetch_op{acquire}(X,-,1)
-atomic_fetch_dec_release(X) __atomic_fetch_op{release}(X,-,1)
-
-atomic_xchg(X,V) __xchg{mb}(X,V)
-atomic_xchg_relaxed(X,V) __xchg{once}(X,V)
-atomic_xchg_release(X,V) __xchg{release}(X,V)
-atomic_xchg_acquire(X,V) __xchg{acquire}(X,V)
-atomic_cmpxchg(X,V,W) __cmpxchg{mb}(X,V,W)
-atomic_cmpxchg_relaxed(X,V,W) __cmpxchg{once}(X,V,W)
-atomic_cmpxchg_acquire(X,V,W) __cmpxchg{acquire}(X,V,W)
-atomic_cmpxchg_release(X,V,W) __cmpxchg{release}(X,V,W)
-
-atomic_sub_and_test(V,X) __atomic_op_return{mb}(X,-,V) == 0
-atomic_dec_and_test(X) __atomic_op_return{mb}(X,-,1) == 0
-atomic_inc_and_test(X) __atomic_op_return{mb}(X,+,1) == 0
-atomic_add_negative(V,X) __atomic_op_return{mb}(X,+,V) < 0
-atomic_add_negative_relaxed(V,X) __atomic_op_return{once}(X,+,V) < 0
-atomic_add_negative_acquire(V,X) __atomic_op_return{acquire}(X,+,V) < 0
-atomic_add_negative_release(V,X) __atomic_op_return{release}(X,+,V) < 0
-
-atomic_fetch_andnot(V,X) __atomic_fetch_op{mb}(X,&~,V)
-atomic_fetch_andnot_acquire(V,X) __atomic_fetch_op{acquire}(X,&~,V)
-atomic_fetch_andnot_release(V,X) __atomic_fetch_op{release}(X,&~,V)
-atomic_fetch_andnot_relaxed(V,X) __atomic_fetch_op{once}(X,&~,V)
+atomic_add_return(V,X) __atomic_op_return{MB}(X,+,V)
+atomic_add_return_relaxed(V,X) __atomic_op_return{ONCE}(X,+,V)
+atomic_add_return_acquire(V,X) __atomic_op_return{ACQUIRE}(X,+,V)
+atomic_add_return_release(V,X) __atomic_op_return{RELEASE}(X,+,V)
+atomic_fetch_add(V,X) __atomic_fetch_op{MB}(X,+,V)
+atomic_fetch_add_relaxed(V,X) __atomic_fetch_op{ONCE}(X,+,V)
+atomic_fetch_add_acquire(V,X) __atomic_fetch_op{ACQUIRE}(X,+,V)
+atomic_fetch_add_release(V,X) __atomic_fetch_op{RELEASE}(X,+,V)
+
+atomic_fetch_and(V,X) __atomic_fetch_op{MB}(X,&,V)
+atomic_fetch_and_relaxed(V,X) __atomic_fetch_op{ONCE}(X,&,V)
+atomic_fetch_and_acquire(V,X) __atomic_fetch_op{ACQUIRE}(X,&,V)
+atomic_fetch_and_release(V,X) __atomic_fetch_op{RELEASE}(X,&,V)
+
+atomic_fetch_or(V,X) __atomic_fetch_op{MB}(X,|,V)
+atomic_fetch_or_relaxed(V,X) __atomic_fetch_op{ONCE}(X,|,V)
+atomic_fetch_or_acquire(V,X) __atomic_fetch_op{ACQUIRE}(X,|,V)
+atomic_fetch_or_release(V,X) __atomic_fetch_op{RELEASE}(X,|,V)
+
+atomic_fetch_xor(V,X) __atomic_fetch_op{MB}(X,^,V)
+atomic_fetch_xor_relaxed(V,X) __atomic_fetch_op{ONCE}(X,^,V)
+atomic_fetch_xor_acquire(V,X) __atomic_fetch_op{ACQUIRE}(X,^,V)
+atomic_fetch_xor_release(V,X) __atomic_fetch_op{RELEASE}(X,^,V)
+
+atomic_inc_return(X) __atomic_op_return{MB}(X,+,1)
+atomic_inc_return_relaxed(X) __atomic_op_return{ONCE}(X,+,1)
+atomic_inc_return_acquire(X) __atomic_op_return{ACQUIRE}(X,+,1)
+atomic_inc_return_release(X) __atomic_op_return{RELEASE}(X,+,1)
+atomic_fetch_inc(X) __atomic_fetch_op{MB}(X,+,1)
+atomic_fetch_inc_relaxed(X) __atomic_fetch_op{ONCE}(X,+,1)
+atomic_fetch_inc_acquire(X) __atomic_fetch_op{ACQUIRE}(X,+,1)
+atomic_fetch_inc_release(X) __atomic_fetch_op{RELEASE}(X,+,1)
+
+atomic_sub_return(V,X) __atomic_op_return{MB}(X,-,V)
+atomic_sub_return_relaxed(V,X) __atomic_op_return{ONCE}(X,-,V)
+atomic_sub_return_acquire(V,X) __atomic_op_return{ACQUIRE}(X,-,V)
+atomic_sub_return_release(V,X) __atomic_op_return{RELEASE}(X,-,V)
+atomic_fetch_sub(V,X) __atomic_fetch_op{MB}(X,-,V)
+atomic_fetch_sub_relaxed(V,X) __atomic_fetch_op{ONCE}(X,-,V)
+atomic_fetch_sub_acquire(V,X) __atomic_fetch_op{ACQUIRE}(X,-,V)
+atomic_fetch_sub_release(V,X) __atomic_fetch_op{RELEASE}(X,-,V)
+
+atomic_dec_return(X) __atomic_op_return{MB}(X,-,1)
+atomic_dec_return_relaxed(X) __atomic_op_return{ONCE}(X,-,1)
+atomic_dec_return_acquire(X) __atomic_op_return{ACQUIRE}(X,-,1)
+atomic_dec_return_release(X) __atomic_op_return{RELEASE}(X,-,1)
+atomic_fetch_dec(X) __atomic_fetch_op{MB}(X,-,1)
+atomic_fetch_dec_relaxed(X) __atomic_fetch_op{ONCE}(X,-,1)
+atomic_fetch_dec_acquire(X) __atomic_fetch_op{ACQUIRE}(X,-,1)
+atomic_fetch_dec_release(X) __atomic_fetch_op{RELEASE}(X,-,1)
+
+atomic_xchg(X,V) __xchg{MB}(X,V)
+atomic_xchg_relaxed(X,V) __xchg{ONCE}(X,V)
+atomic_xchg_release(X,V) __xchg{RELEASE}(X,V)
+atomic_xchg_acquire(X,V) __xchg{ACQUIRE}(X,V)
+atomic_cmpxchg(X,V,W) __cmpxchg{MB}(X,V,W)
+atomic_cmpxchg_relaxed(X,V,W) __cmpxchg{ONCE}(X,V,W)
+atomic_cmpxchg_acquire(X,V,W) __cmpxchg{ACQUIRE}(X,V,W)
+atomic_cmpxchg_release(X,V,W) __cmpxchg{RELEASE}(X,V,W)
+
+atomic_sub_and_test(V,X) __atomic_op_return{MB}(X,-,V) == 0
+atomic_dec_and_test(X) __atomic_op_return{MB}(X,-,1) == 0
+atomic_inc_and_test(X) __atomic_op_return{MB}(X,+,1) == 0
+atomic_add_negative(V,X) __atomic_op_return{MB}(X,+,V) < 0
+atomic_add_negative_relaxed(V,X) __atomic_op_return{ONCE}(X,+,V) < 0
+atomic_add_negative_acquire(V,X) __atomic_op_return{ACQUIRE}(X,+,V) < 0
+atomic_add_negative_release(V,X) __atomic_op_return{RELEASE}(X,+,V) < 0
+
+atomic_fetch_andnot(V,X) __atomic_fetch_op{MB}(X,&~,V)
+atomic_fetch_andnot_acquire(V,X) __atomic_fetch_op{ACQUIRE}(X,&~,V)
+atomic_fetch_andnot_release(V,X) __atomic_fetch_op{RELEASE}(X,&~,V)
+atomic_fetch_andnot_relaxed(V,X) __atomic_fetch_op{ONCE}(X,&~,V)
--
2.34.1

Next message: Rob Herring: "Re: [PATCH 2/3] of: Add missing locking to of_(bus_)?n_(size|addr)_cells()"
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In reply to: Jonas Oberhauser: "Re: [PATCHv2 3/4] tools/memory-model: Define effect of Mb tags on RMWs in tools/..."
Next in thread: Jonas Oberhauser: "[PATCHv2 1/4] tools/memory-model: Legitimize current use of tags in LKMM macros"
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