xref: /linux/tools/memory-model/Documentation/herd-representation.txt (revision c532de5a67a70f8533d495f8f2aaa9a0491c3ad0)
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# Disclaimer.  The table includes representations of "add" and "and" operations;
22# corresponding/identical representations of "sub", "inc", "dec" and "or", "xor",
23# "andnot" operations are omitted.
24#
25    ------------------------------------------------------------------------------
26    |                        C macro | Events                                    |
27    ------------------------------------------------------------------------------
28    |                    Non-RMW ops |                                           |
29    ------------------------------------------------------------------------------
30    |                      READ_ONCE | R[once]                                   |
31    |                    atomic_read |                                           |
32    |                     WRITE_ONCE | W[once]                                   |
33    |                     atomic_set |                                           |
34    |               smp_load_acquire | R[acquire]                                |
35    |            atomic_read_acquire |                                           |
36    |              smp_store_release | W[release]                                |
37    |             atomic_set_release |                                           |
38    |                   smp_store_mb | W[once] ->po F[mb]                        |
39    |                         smp_mb | F[mb]                                     |
40    |                        smp_rmb | F[rmb]                                    |
41    |                        smp_wmb | F[wmb]                                    |
42    |          smp_mb__before_atomic | F[before-atomic]                          |
43    |           smp_mb__after_atomic | F[after-atomic]                           |
44    |                    spin_unlock | UL                                        |
45    |                 spin_is_locked | On success: RL                            |
46    |                                | On failure: RU                            |
47    |         smp_mb__after_spinlock | F[after-spinlock]                         |
48    |      smp_mb__after_unlock_lock | F[after-unlock-lock]                      |
49    |                  rcu_read_lock | F[rcu-lock]                               |
50    |                rcu_read_unlock | F[rcu-unlock]                             |
51    |                synchronize_rcu | F[sync-rcu]                               |
52    |                rcu_dereference | R[once]                                   |
53    |             rcu_assign_pointer | W[release]                                |
54    |                 srcu_read_lock | R[srcu-lock]                              |
55    |                 srcu_down_read |                                           |
56    |               srcu_read_unlock | W[srcu-unlock]                            |
57    |                   srcu_up_read |                                           |
58    |               synchronize_srcu | SRCU[sync-srcu]                           |
59    | smp_mb__after_srcu_read_unlock | F[after-srcu-read-unlock]                 |
60    ------------------------------------------------------------------------------
61    |       RMW ops w/o return value |                                           |
62    ------------------------------------------------------------------------------
63    |                     atomic_add | R*[noreturn] ->rmw W*[once]               |
64    |                     atomic_and |                                           |
65    |                      spin_lock | LKR ->po LKW                              |
66    ------------------------------------------------------------------------------
67    |        RMW ops w/ return value |                                           |
68    ------------------------------------------------------------------------------
69    |              atomic_add_return | F[mb] ->po R*[once]                       |
70    |                                |     ->rmw W*[once] ->po F[mb]             |
71    |               atomic_fetch_add |                                           |
72    |               atomic_fetch_and |                                           |
73    |                    atomic_xchg |                                           |
74    |                           xchg |                                           |
75    |            atomic_add_negative |                                           |
76    |      atomic_add_return_relaxed | R*[once] ->rmw W*[once]                   |
77    |       atomic_fetch_add_relaxed |                                           |
78    |       atomic_fetch_and_relaxed |                                           |
79    |            atomic_xchg_relaxed |                                           |
80    |                   xchg_relaxed |                                           |
81    |    atomic_add_negative_relaxed |                                           |
82    |      atomic_add_return_acquire | R*[acquire] ->rmw W*[once]                |
83    |       atomic_fetch_add_acquire |                                           |
84    |       atomic_fetch_and_acquire |                                           |
85    |            atomic_xchg_acquire |                                           |
86    |                   xchg_acquire |                                           |
87    |    atomic_add_negative_acquire |                                           |
88    |      atomic_add_return_release | R*[once] ->rmw W*[release]                |
89    |       atomic_fetch_add_release |                                           |
90    |       atomic_fetch_and_release |                                           |
91    |            atomic_xchg_release |                                           |
92    |                   xchg_release |                                           |
93    |    atomic_add_negative_release |                                           |
94    ------------------------------------------------------------------------------
95    |            Conditional RMW ops |                                           |
96    ------------------------------------------------------------------------------
97    |                 atomic_cmpxchg | On success: F[mb] ->po R*[once]           |
98    |                                |                 ->rmw W*[once] ->po F[mb] |
99    |                                | On failure: R*[once]                      |
100    |                        cmpxchg |                                           |
101    |              atomic_add_unless |                                           |
102    |         atomic_cmpxchg_relaxed | On success: R*[once] ->rmw W*[once]       |
103    |                                | On failure: R*[once]                      |
104    |         atomic_cmpxchg_acquire | On success: R*[acquire] ->rmw W*[once]    |
105    |                                | On failure: R*[once]                      |
106    |         atomic_cmpxchg_release | On success: R*[once] ->rmw W*[release]    |
107    |                                | On failure: R*[once]                      |
108    |                   spin_trylock | On success: LKR ->po LKW                  |
109    |                                | On failure: LF                            |
110    ------------------------------------------------------------------------------
111