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/ > --- 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. > --- 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/ > --- 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/ > --- 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/ > + * 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. > --- 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/ > --- 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? > --- 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/./?/ > --- 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/ > --- 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/ > --- 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. Alan
