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Diffstat (limited to 'tools/memory-model/README')
| -rw-r--r-- | tools/memory-model/README | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/tools/memory-model/README b/tools/memory-model/README index 0f2c366518c6..2b87f3971548 100644 --- a/tools/memory-model/README +++ b/tools/memory-model/README @@ -20,13 +20,17 @@ that litmus test to be exercised within the Linux kernel. REQUIREMENTS ============ -Version 7.49 of the "herd7" and "klitmus7" tools must be downloaded -separately: +Version 7.52 or higher of the "herd7" and "klitmus7" tools must be +downloaded separately: https://github.com/herd/herdtools7 See "herdtools7/INSTALL.md" for installation instructions. +Note that although these tools usually provide backwards compatibility, +this is not absolutely guaranteed. Therefore, if a later version does +not work, please try using the exact version called out above. + ================== BASIC USAGE: HERD7 @@ -221,8 +225,29 @@ The Linux-kernel memory model has the following limitations: additional call_rcu() process to the site of the emulated rcu-barrier(). - e. Sleepable RCU (SRCU) is not modeled. It can be - emulated, but perhaps not simply. + e. Although sleepable RCU (SRCU) is now modeled, there + are some subtle differences between its semantics and + those in the Linux kernel. For example, the kernel + might interpret the following sequence as two partially + overlapping SRCU read-side critical sections: + + 1 r1 = srcu_read_lock(&my_srcu); + 2 do_something_1(); + 3 r2 = srcu_read_lock(&my_srcu); + 4 do_something_2(); + 5 srcu_read_unlock(&my_srcu, r1); + 6 do_something_3(); + 7 srcu_read_unlock(&my_srcu, r2); + + In contrast, LKMM will interpret this as a nested pair of + SRCU read-side critical sections, with the outer critical + section spanning lines 1-7 and the inner critical section + spanning lines 3-5. + + This difference would be more of a concern had anyone + identified a reasonable use case for partially overlapping + SRCU read-side critical sections. For more information, + please see: https://paulmck.livejournal.com/40593.html f. Reader-writer locking is not modeled. It can be emulated in litmus tests using atomic read-modify-write |