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authorAlan Stern <stern@rowland.harvard.edu>2018-02-20 15:25:10 -0800
committerIngo Molnar <mingo@kernel.org>2018-02-21 09:58:15 +0100
commit556bb7d252ae42d4653557325670e665087c38ad (patch)
treee57c5bd41de47f4ff5c19f406f063bda54b163fd /tools/memory-model/litmus-tests
parent8f7f2fbd00898deaf01e05a00095411811befd64 (diff)
downloadtip-556bb7d252ae42d4653557325670e665087c38ad.tar.gz
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tools/memory-model: Add a S lock-based external-view litmus test
This commit adds a litmus test in which P0() and P1() form a lock-based S litmus test, with the addition of P2(), which observes P0()'s and P1()'s accesses with a full memory barrier but without the lock. This litmus test asks whether writes carried out by two different processes under the same lock will be seen in order by a third process not holding that lock. The answer to this question is "yes" for all architectures supporting the Linux kernel, but is "no" according to the current version of LKMM. A patch to LKMM is under development. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.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: nborisov@suse.com Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1519169112-20593-10-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/memory-model/litmus-tests')
-rw-r--r--tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus41
1 files changed, 41 insertions, 0 deletions
diff --git a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
new file mode 100644
index 000000000000..7a39a0aaa976
--- /dev/null
+++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus
@@ -0,0 +1,41 @@
+C ISA2+pooncelock+pooncelock+pombonce.litmus
+
+(*
+ * Result: Sometimes
+ *
+ * This test shows that the ordering provided by a lock-protected S
+ * litmus test (P0() and P1()) are not visible to external process P2().
+ * This is likely to change soon.
+ *)
+
+{}
+
+P0(int *x, int *y, spinlock_t *mylock)
+{
+ spin_lock(mylock);
+ WRITE_ONCE(*x, 1);
+ WRITE_ONCE(*y, 1);
+ spin_unlock(mylock);
+}
+
+P1(int *y, int *z, spinlock_t *mylock)
+{
+ int r0;
+
+ spin_lock(mylock);
+ r0 = READ_ONCE(*y);
+ WRITE_ONCE(*z, 1);
+ spin_unlock(mylock);
+}
+
+P2(int *x, int *z)
+{
+ int r1;
+ int r2;
+
+ r2 = READ_ONCE(*z);
+ smp_mb();
+ r1 = READ_ONCE(*x);
+}
+
+exists (1:r0=1 /\ 2:r2=1 /\ 2:r1=0)