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authorAlan Stern <stern@rowland.harvard.edu>2018-11-15 11:20:37 -0500
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-03-18 10:27:52 -0700
commita3f600d92da564ad35f237c8aeab268ca49377cc (patch)
tree8b5cbb5e49d7b0556f2fdd1faf9667810c4d1941 /tools/memory-model
parent284749b0aebbf3ab26ff92198545aea36165f6bf (diff)
tools/memory-model: Add SRCU support
Add support for SRCU. Herd creates srcu events and linux-kernel.def associates them with three possible annotations (srcu-lock, srcu-unlock, and sync-srcu) corresponding to the API routines srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu(). The linux-kernel.bell file now declares the annotations and determines matching lock/unlock pairs delimiting SRCU read-side critical sections, and it also checks for synchronize_srcu() calls inside an RCU critical section (which would generate a "sleeping in atomic context" error in real kernel code). The linux-kernel.cat file now adds SRCU-induced ordering, analogous to the existing RCU-induced ordering, to the gp and rcu-fence relations. Curiously enough, these small changes to the model's .cat code are all that is needed to describe SRCU. Portions of this patch (linux-kernel.def and the first hunk in linux-kernel.bell) were written by Luc Maranget. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Luc Maranget <luc.maranget@inria.fr> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Diffstat (limited to 'tools/memory-model')
-rw-r--r--tools/memory-model/linux-kernel.bell25
-rw-r--r--tools/memory-model/linux-kernel.cat18
-rw-r--r--tools/memory-model/linux-kernel.def5
3 files changed, 44 insertions, 4 deletions
diff --git a/tools/memory-model/linux-kernel.bell b/tools/memory-model/linux-kernel.bell
index 353c8d68e030..9c42cd9ddcb4 100644
--- a/tools/memory-model/linux-kernel.bell
+++ b/tools/memory-model/linux-kernel.bell
@@ -33,6 +33,12 @@ enum Barriers = 'wmb (*smp_wmb*) ||
'after-unlock-lock (*smp_mb__after_unlock_lock*)
instructions F[Barriers]
+(* SRCU *)
+enum SRCU = 'srcu-lock || 'srcu-unlock || 'sync-srcu
+instructions SRCU[SRCU]
+(* All srcu events *)
+let Srcu = Srcu-lock | Srcu-unlock | Sync-srcu
+
(* Compute matching pairs of nested Rcu-lock and Rcu-unlock *)
let rcu-rscs = let rec
unmatched-locks = Rcu-lock \ domain(matched)
@@ -48,3 +54,22 @@ let rcu-rscs = let rec
(* Validate nesting *)
flag ~empty Rcu-lock \ domain(rcu-rscs) as unbalanced-rcu-locking
flag ~empty Rcu-unlock \ range(rcu-rscs) as unbalanced-rcu-locking
+
+(* Compute matching pairs of nested Srcu-lock and Srcu-unlock *)
+let srcu-rscs = let rec
+ unmatched-locks = Srcu-lock \ domain(matched)
+ and unmatched-unlocks = Srcu-unlock \ range(matched)
+ and unmatched = unmatched-locks | unmatched-unlocks
+ and unmatched-po = ([unmatched] ; po ; [unmatched]) & loc
+ and unmatched-locks-to-unlocks =
+ ([unmatched-locks] ; po ; [unmatched-unlocks]) & loc
+ and matched = matched | (unmatched-locks-to-unlocks \
+ (unmatched-po ; unmatched-po))
+ in matched
+
+(* Validate nesting *)
+flag ~empty Srcu-lock \ domain(srcu-rscs) as unbalanced-srcu-locking
+flag ~empty Srcu-unlock \ range(srcu-rscs) as unbalanced-srcu-locking
+
+(* Check for use of synchronize_srcu() inside an RCU critical section *)
+flag ~empty rcu-rscs & (po ; [Sync-srcu] ; po) as invalid-sleep
diff --git a/tools/memory-model/linux-kernel.cat b/tools/memory-model/linux-kernel.cat
index b8e6197f05af..8dcb37835b61 100644
--- a/tools/memory-model/linux-kernel.cat
+++ b/tools/memory-model/linux-kernel.cat
@@ -33,7 +33,7 @@ let mb = ([M] ; fencerel(Mb) ; [M]) |
([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) |
([M] ; po ; [UL] ; (co | po) ; [LKW] ;
fencerel(After-unlock-lock) ; [M])
-let gp = po ; [Sync-rcu] ; po?
+let gp = po ; [Sync-rcu | Sync-srcu] ; po?
let strong-fence = mb | gp
@@ -92,15 +92,18 @@ acyclic pb as propagation
(*
* Effects of read-side critical sections proceed from the rcu_read_unlock()
- * backwards on the one hand, and from the rcu_read_lock() forwards on the
- * other hand.
+ * or srcu_read_unlock() backwards on the one hand, and from the
+ * rcu_read_lock() or srcu_read_lock() forwards on the other hand.
*
* In the definition of rcu-fence below, the po term at the left-hand side
* of each disjunct and the po? term at the right-hand end have been factored
* out. They have been moved into the definitions of rcu-link and rb.
+ * This was necessary in order to apply the "& loc" tests correctly.
*)
let rcu-gp = [Sync-rcu] (* Compare with gp *)
+let srcu-gp = [Sync-srcu]
let rcu-rscsi = rcu-rscs^-1
+let srcu-rscsi = srcu-rscs^-1
(*
* The synchronize_rcu() strong fence is special in that it can order not
@@ -112,12 +115,19 @@ let rcu-link = po? ; hb* ; pb* ; prop ; po
(*
* Any sequence containing at least as many grace periods as RCU read-side
* critical sections (joined by rcu-link) acts as a generalized strong fence.
+ * Likewise for SRCU grace periods and read-side critical sections, provided
+ * the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same
+ * struct srcu_struct location.
*)
-let rec rcu-fence = rcu-gp |
+let rec rcu-fence = rcu-gp | srcu-gp |
(rcu-gp ; rcu-link ; rcu-rscsi) |
+ ((srcu-gp ; rcu-link ; srcu-rscsi) & loc) |
(rcu-rscsi ; rcu-link ; rcu-gp) |
+ ((srcu-rscsi ; rcu-link ; srcu-gp) & loc) |
(rcu-gp ; rcu-link ; rcu-fence ; rcu-link ; rcu-rscsi) |
+ ((srcu-gp ; rcu-link ; rcu-fence ; rcu-link ; srcu-rscsi) & loc) |
(rcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; rcu-gp) |
+ ((srcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; srcu-gp) & loc) |
(rcu-fence ; rcu-link ; rcu-fence)
(* rb orders instructions just as pb does *)
diff --git a/tools/memory-model/linux-kernel.def b/tools/memory-model/linux-kernel.def
index b27911cc087d..1d6a120cde14 100644
--- a/tools/memory-model/linux-kernel.def
+++ b/tools/memory-model/linux-kernel.def
@@ -47,6 +47,11 @@ rcu_read_unlock() { __fence{rcu-unlock}; }
synchronize_rcu() { __fence{sync-rcu}; }
synchronize_rcu_expedited() { __fence{sync-rcu}; }
+// SRCU
+srcu_read_lock(X) __srcu{srcu-lock}(X)
+srcu_read_unlock(X,Y) { __srcu{srcu-unlock}(X); }
+synchronize_srcu(X) { __srcu{sync-srcu}(X); }
+
// Atomic
atomic_read(X) READ_ONCE(*X)
atomic_set(X,V) { WRITE_ONCE(*X,V); }