On Sun, Feb 04, 2018 at 11:37:59AM -0500, Alan Stern wrote: > On Sun, 4 Feb 2018, Paul E. McKenney wrote: > > > --- a/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus > > +++ b/tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus > > @@ -1,5 +1,11 @@ > > C CoRW+poonceonce+Once > > > > +(* > > + * Test of read-write coherence, that is, whether or not a read from a > > + * given variable followed by a write to that same variable are ordered. > > The syntax of this sentence is a little tortured. Suggestion: > > ... whether or not a read from a given variable and a later > write to that same variable are ordered. > > > + * This should be ordered, that is, this test should be forbidden. > > s/This/They/ Good catches, both changed as suggested. > > --- a/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus > > +++ b/tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus > > @@ -1,5 +1,11 @@ > > C CoWR+poonceonce+Once > > > > +(* > > + * Test of write-read coherence, that is, whether or not a write to a > > + * given variable followed by a read from that same variable are ordered. > > Same syntax issue as above. Analogous fixed applied! > > --- a/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus > > +++ b/tools/memory-model/litmus-tests/ISA2+poonceonces.litmus > > @@ -1,5 +1,13 @@ > > C ISA2+poonceonces > > > > +(* > > + * Given a release-acquire chain ordering the first process's store > > + * against the last process's load, is ordering preserved if all of the > > + * smp_store_release() invocations be replaced by WRITE_ONCE() and all > > s/be/are/ > > > + * of the smp_load_acquire() invocations be replaced by READ_ONCE()? > > s/be/are/ Good eyes, fixed! > > --- a/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus > > +++ b/tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus > > @@ -1,5 +1,14 @@ > > C LB+ctrlonceonce+mbonceonce > > > > +(* > > + * This litmus test demonstrates that lightweight ordering suffices for > > + * the load-buffering pattern, in other words, preventing all processes > > + * reading from the preceding process's write. In this example, the > > + * combination of a control dependency and a full memory barrier are to do > > s/are to/are enough to/ Ditto! > > --- a/tools/memory-model/litmus-tests/MP+polocks.litmus > > +++ b/tools/memory-model/litmus-tests/MP+polocks.litmus > > @@ -1,5 +1,14 @@ > > C MP+polocks > > > > +(* > > + * This litmus test demonstrates how lock acquisitions and releases can > > + * stand in for smp_load_acquire() and smp_store_release(), respectively. > > + * In other words, when holding a given lock (or indeed after relaasing a > > s/relaasing/releasing/ > > > + * given lock), a CPU is not only guaranteed to see the accesses that other > > + * CPOs made while previously holding that lock, it are also guaranteed > > s/CPO/CPU/ > s/are/is/ Andrea beat you to the first two of these three, but fixed. ;-) > > + * to see all prior accesses by those other CPUs. > > Doesn't say whether the test should be allowed. This is true of several > other litmus tests too. Added the "Forbidden". You know, I should use the machine-generated syntax that my scripts recognize, shouldn't I? Doing that as well. > > --- a/tools/memory-model/litmus-tests/MP+porevlocks.litmus > > +++ b/tools/memory-model/litmus-tests/MP+porevlocks.litmus > > @@ -1,5 +1,14 @@ > > C MP+porevlocks > > > > +(* > > + * This litmus test demonstrates how lock acquisitions and releases can > > + * stand in for smp_load_acquire() and smp_store_release(), respectively. > > + * In other words, when holding a given lock (or indeed after relaasing a > > s/relaasing/releasing > > > + * given lock), a CPU is not only guaranteed to see the accesses that other > > + * CPOs made while previously holding that lock, it are also guaranteed > > s/CPO/CPU/ > s/are/is/ Fixed! > > --- a/tools/memory-model/litmus-tests/R+poonceonces.litmus > > +++ b/tools/memory-model/litmus-tests/R+poonceonces.litmus > > @@ -1,5 +1,11 @@ > > C R+poonceonces > > > > +(* > > + * This is the unordered (via smp_mb()) version of one of the classic > > Does "unordered (via smp_mb())" mean that the test uses smp_mb() to > "unorder" the accesses, or does it mean that the test doesn't use smp_mb() > to order the accesses? That is a bit ambiguous... Though I would be interested in seeing a litmus test that really did use smp_mb() to unorder the accesses! How about the following? * Result: Sometimes * * This is the unordered (thus lacking smp_mb()) version of one of the * classic counterintuitive litmus tests that illustrates the effects of * store propagation delays. > > --- a/tools/memory-model/litmus-tests/S+poonceonces.litmus > > +++ b/tools/memory-model/litmus-tests/S+poonceonces.litmus > > @@ -1,5 +1,13 @@ > > C S+poonceonces > > > > +(* > > + * Starting with a two-process release-acquire chain ordering P0()'s > > + * first store against P1()'s final load, if the smp_store_release() > > + * is replaced by WRITE_ONCE() and the smp_load_acquire() replaced by > > + * READ_ONCE(), is ordering preserved. The answer is "of course not!", > > s/./?/ Good eyes, fixed! > > --- a/tools/memory-model/litmus-tests/SB+mbonceonces.litmus > > +++ b/tools/memory-model/litmus-tests/SB+mbonceonces.litmus > > @@ -1,5 +1,12 @@ > > C SB+mbonceonces > > > > +(* > > + * This litmus test demonstrates that full memory barriers suffice to > > + * order the store-buffering pattern, where each process writes to the > > + * variable that the preceding process read. (Locking and RCU can also > > s/read/reads/ Ditto! > > --- a/tools/memory-model/litmus-tests/SB+poonceonces.litmus > > +++ b/tools/memory-model/litmus-tests/SB+poonceonces.litmus > > @@ -1,5 +1,11 @@ > > C SB+poonceonces > > > > +(* > > + * This litmus test demonstrates that at least some ordering is required > > + * to order the store-buffering pattern, where each process writes to the > > + * variable that the preceding process read. This test should be allowed. > > s/read/reads/ And ditto again! (Hey, at least I was consistent! If you didn't know better, you might even think that I was using copy-and-paste.) > > --- a/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus > > +++ b/tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus > > @@ -1,5 +1,11 @@ > > C Z6.0+pooncelock+pooncelock+pombonce > > > > +(* > > + * 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. > > + *) > > Note that the outcome of this test will be changed by one of the > patches in our "pending" list. I decided to anticipate that change and marked it "Result: Never". ;-) Thanx, Paul
