tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1C RM-broken
2
3(*
4 * Result: DEADLOCK
5 *
6 * This litmus test demonstrates that the old "roach motel" approach
7 * to locking, where code can be freely moved into critical sections,
8 * cannot be used in the Linux kernel.
9 *)
10
11{
12 int x;
13 atomic_t y;
14}
15
16P0(int *x, atomic_t *y, spinlock_t *lck)
17{
18 int r2;
19
20 spin_lock(lck);
21 r2 = atomic_inc_return(y);
22 WRITE_ONCE(*x, 1);
23 spin_unlock(lck);
24}
25
26P1(int *x, atomic_t *y, spinlock_t *lck)
27{
28 int r0;
29 int r1;
30 int r2;
31
32 spin_lock(lck);
33 r0 = READ_ONCE(*x);
34 r1 = READ_ONCE(*x);
35 r2 = atomic_inc_return(y);
36 spin_unlock(lck);
37}
38
39locations [x;0:r2;1:r0;1:r1;1:r2]
40filter (1:r0=0 /\ 1:r1=1)
41exists (1:r2=1)