Commit-ID: 556bb7d252ae42d4653557325670e665087c38ad Gitweb: https://git.kernel.org/tip/556bb7d252ae42d4653557325670e665087c38ad Author: Alan Stern <[email protected]> AuthorDate: Tue, 20 Feb 2018 15:25:10 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 21 Feb 2018 09:58:15 +0100
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 <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Acked-by: Peter Zijlstra <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- ...ce.litmus => ISA2+pooncelock+pooncelock+pombonce.litmus} | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus similarity index 55% copy from tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus copy to tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus index 10a2aa0..7a39a0a 100644 --- a/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus +++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus @@ -1,11 +1,11 @@ -C Z6.0+pooncelock+pooncelock+pombonce +C ISA2+pooncelock+pooncelock+pombonce.litmus (* * Result: Sometimes * - * This example demonstrates that a pair of accesses made by different - * processes each while holding a given lock will not necessarily be - * seen as ordered by a third process not holding that lock. + * 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. *) {} @@ -31,10 +31,11 @@ P1(int *y, int *z, spinlock_t *mylock) P2(int *x, int *z) { int r1; + int r2; - WRITE_ONCE(*z, 2); + r2 = READ_ONCE(*z); smp_mb(); r1 = READ_ONCE(*x); } -exists (1:r0=1 /\ z=2 /\ 2:r1=0) +exists (1:r0=1 /\ 2:r2=1 /\ 2:r1=0)
