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Diffstat (limited to 'Documentation/litmus-tests/locking/DCL-broken.litmus')
| -rw-r--r-- | Documentation/litmus-tests/locking/DCL-broken.litmus | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/litmus-tests/locking/DCL-broken.litmus b/Documentation/litmus-tests/locking/DCL-broken.litmus new file mode 100644 index 000000000000..bfb7ba4316d6 --- /dev/null +++ b/Documentation/litmus-tests/locking/DCL-broken.litmus @@ -0,0 +1,54 @@ +C DCL-broken + +(* + * Result: Sometimes + * + * This litmus test demonstrates more than just locking is required to + * correctly implement double-checked locking. + *) + +{ + int flag; + int data; +} + +P0(int *flag, int *data, spinlock_t *lck) +{ + int r0; + int r1; + int r2; + + r0 = READ_ONCE(*flag); + if (r0 == 0) { + spin_lock(lck); + r1 = READ_ONCE(*flag); + if (r1 == 0) { + WRITE_ONCE(*data, 1); + WRITE_ONCE(*flag, 1); + } + spin_unlock(lck); + } + r2 = READ_ONCE(*data); +} + +P1(int *flag, int *data, spinlock_t *lck) +{ + int r0; + int r1; + int r2; + + r0 = READ_ONCE(*flag); + if (r0 == 0) { + spin_lock(lck); + r1 = READ_ONCE(*flag); + if (r1 == 0) { + WRITE_ONCE(*data, 1); + WRITE_ONCE(*flag, 1); + } + spin_unlock(lck); + } + r2 = READ_ONCE(*data); +} + +locations [flag;data;0:r0;0:r1;1:r0;1:r1] +exists (0:r2=0 \/ 1:r2=0) |