xref: /linux/tools/memory-model/Documentation/herd-representation.txt (revision 4f9786035f9e519db41375818e1d0b5f20da2f10)
1#
2# Legend:
3#	R,	a Load event
4#	W,	a Store event
5#	F,	a Fence event
6#	LKR,	a Lock-Read event
7#	LKW,	a Lock-Write event
8#	UL,	an Unlock event
9#	LF,	a Lock-Fail event
10#	RL,	a Read-Locked event
11#	RU,	a Read-Unlocked event
12#	R*,	a Load event included in RMW
13#	W*,	a Store event included in RMW
14#	SRCU,	a Sleepable-Read-Copy-Update event
15#
16#	po,	a Program-Order link
17#	rmw,	a Read-Modify-Write link - every rmw link is a po link
18#
19# By convention, a blank line in a cell means "same as the preceding line".
20#
21# Note that the syntactic representation does not always match the sets and
22# relations in linux-kernel.cat, due to redefinitions in linux-kernel.bell and
23# lock.cat. For example, the po link between LKR and LKW is upgraded to an rmw
24# link, and W[ACQUIRE] are not included in the Acquire set.
25#
26# Disclaimer.  The table includes representations of "add" and "and" operations;
27# corresponding/identical representations of "sub", "inc", "dec" and "or", "xor",
28# "andnot" operations are omitted.
29#
30    ------------------------------------------------------------------------------
31    |                        C macro | Events                                    |
32    ------------------------------------------------------------------------------
33    |                    Non-RMW ops |                                           |
34    ------------------------------------------------------------------------------
35    |                      READ_ONCE | R[ONCE]                                   |
36    |                    atomic_read |                                           |
37    |                     WRITE_ONCE | W[ONCE]                                   |
38    |                     atomic_set |                                           |
39    |               smp_load_acquire | R[ACQUIRE]                                |
40    |            atomic_read_acquire |                                           |
41    |              smp_store_release | W[RELEASE]                                |
42    |             atomic_set_release |                                           |
43    |                   smp_store_mb | W[ONCE] ->po F[MB]                        |
44    |                         smp_mb | F[MB]                                     |
45    |                        smp_rmb | F[rmb]                                    |
46    |                        smp_wmb | F[wmb]                                    |
47    |          smp_mb__before_atomic | F[before-atomic]                          |
48    |           smp_mb__after_atomic | F[after-atomic]                           |
49    |                    spin_unlock | UL                                        |
50    |                 spin_is_locked | On success: RL                            |
51    |                                | On failure: RU                            |
52    |         smp_mb__after_spinlock | F[after-spinlock]                         |
53    |      smp_mb__after_unlock_lock | F[after-unlock-lock]                      |
54    |                  rcu_read_lock | F[rcu-lock]                               |
55    |                rcu_read_unlock | F[rcu-unlock]                             |
56    |                synchronize_rcu | F[sync-rcu]                               |
57    |                rcu_dereference | R[ONCE]                                   |
58    |             rcu_assign_pointer | W[RELEASE]                                |
59    |                 srcu_read_lock | R[srcu-lock]                              |
60    |                 srcu_down_read |                                           |
61    |               srcu_read_unlock | W[srcu-unlock]                            |
62    |                   srcu_up_read |                                           |
63    |               synchronize_srcu | SRCU[sync-srcu]                           |
64    | smp_mb__after_srcu_read_unlock | F[after-srcu-read-unlock]                 |
65    ------------------------------------------------------------------------------
66    |       RMW ops w/o return value |                                           |
67    ------------------------------------------------------------------------------
68    |                     atomic_add | R*[NORETURN] ->rmw W*[NORETURN]           |
69    |                     atomic_and |                                           |
70    |                      spin_lock | LKR ->po LKW                              |
71    ------------------------------------------------------------------------------
72    |        RMW ops w/ return value |                                           |
73    ------------------------------------------------------------------------------
74    |              atomic_add_return | R*[MB] ->rmw W*[MB]                       |
75    |               atomic_fetch_add |                                           |
76    |               atomic_fetch_and |                                           |
77    |                    atomic_xchg |                                           |
78    |                           xchg |                                           |
79    |            atomic_add_negative |                                           |
80    |      atomic_add_return_relaxed | R*[ONCE] ->rmw W*[ONCE]                   |
81    |       atomic_fetch_add_relaxed |                                           |
82    |       atomic_fetch_and_relaxed |                                           |
83    |            atomic_xchg_relaxed |                                           |
84    |                   xchg_relaxed |                                           |
85    |    atomic_add_negative_relaxed |                                           |
86    |      atomic_add_return_acquire | R*[ACQUIRE] ->rmw W*[ACQUIRE]             |
87    |       atomic_fetch_add_acquire |                                           |
88    |       atomic_fetch_and_acquire |                                           |
89    |            atomic_xchg_acquire |                                           |
90    |                   xchg_acquire |                                           |
91    |    atomic_add_negative_acquire |                                           |
92    |      atomic_add_return_release | R*[RELEASE] ->rmw W*[RELEASE]             |
93    |       atomic_fetch_add_release |                                           |
94    |       atomic_fetch_and_release |                                           |
95    |            atomic_xchg_release |                                           |
96    |                   xchg_release |                                           |
97    |    atomic_add_negative_release |                                           |
98    ------------------------------------------------------------------------------
99    |            Conditional RMW ops |                                           |
100    ------------------------------------------------------------------------------
101    |                 atomic_cmpxchg | On success: R*[MB] ->rmw W*[MB]           |
102    |                                | On failure: R*[MB]                        |
103    |                        cmpxchg |                                           |
104    |              atomic_add_unless |                                           |
105    |         atomic_cmpxchg_relaxed | On success: R*[ONCE] ->rmw W*[ONCE]       |
106    |                                | On failure: R*[ONCE]                      |
107    |         atomic_cmpxchg_acquire | On success: R*[ACQUIRE] ->rmw W*[ACQUIRE] |
108    |                                | On failure: R*[ACQUIRE]                   |
109    |         atomic_cmpxchg_release | On success: R*[RELEASE] ->rmw W*[RELEASE] |
110    |                                | On failure: R*[RELEASE]                   |
111    |                   spin_trylock | On success: LKR ->po LKW                  |
112    |                                | On failure: LF                            |
113    ------------------------------------------------------------------------------
114