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author | Linus Torvalds <torvalds@linux-foundation.org> | 2018-10-23 14:08:53 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-10-23 14:08:53 +0200 |
commit | 0200fbdd431519d730b5d399a12840ec832b27cc (patch) | |
tree | 2b58f9e24b61b00e0550f106c95bfabc3b52cfdd /tools/memory-model/litmus-tests | |
parent | Merge branch 'efi-core-for-linus' of git://git.kernel.org/pub/scm/linux/kerne... (diff) | |
parent | locking/lockdep: Make global debug_locks* variables read-mostly (diff) | |
download | linux-0200fbdd431519d730b5d399a12840ec832b27cc.tar.xz linux-0200fbdd431519d730b5d399a12840ec832b27cc.zip |
Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking and misc x86 updates from Ingo Molnar:
"Lots of changes in this cycle - in part because locking/core attracted
a number of related x86 low level work which was easier to handle in a
single tree:
- Linux Kernel Memory Consistency Model updates (Alan Stern, Paul E.
McKenney, Andrea Parri)
- lockdep scalability improvements and micro-optimizations (Waiman
Long)
- rwsem improvements (Waiman Long)
- spinlock micro-optimization (Matthew Wilcox)
- qspinlocks: Provide a liveness guarantee (more fairness) on x86.
(Peter Zijlstra)
- Add support for relative references in jump tables on arm64, x86
and s390 to optimize jump labels (Ard Biesheuvel, Heiko Carstens)
- Be a lot less permissive on weird (kernel address) uaccess faults
on x86: BUG() when uaccess helpers fault on kernel addresses (Jann
Horn)
- macrofy x86 asm statements to un-confuse the GCC inliner. (Nadav
Amit)
- ... and a handful of other smaller changes as well"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
locking/lockdep: Make global debug_locks* variables read-mostly
locking/lockdep: Fix debug_locks off performance problem
locking/pvqspinlock: Extend node size when pvqspinlock is configured
locking/qspinlock_stat: Count instances of nested lock slowpaths
locking/qspinlock, x86: Provide liveness guarantee
x86/asm: 'Simplify' GEN_*_RMWcc() macros
locking/qspinlock: Rework some comments
locking/qspinlock: Re-order code
locking/lockdep: Remove duplicated 'lock_class_ops' percpu array
x86/defconfig: Enable CONFIG_USB_XHCI_HCD=y
futex: Replace spin_is_locked() with lockdep
locking/lockdep: Make class->ops a percpu counter and move it under CONFIG_DEBUG_LOCKDEP=y
x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs
x86/cpufeature: Macrofy inline assembly code to work around GCC inlining bugs
x86/extable: Macrofy inline assembly code to work around GCC inlining bugs
x86/paravirt: Work around GCC inlining bugs when compiling paravirt ops
x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs
x86/alternatives: Macrofy lock prefixes to work around GCC inlining bugs
x86/refcount: Work around GCC inlining bug
x86/objtool: Use asm macros to work around GCC inlining bugs
...
Diffstat (limited to '')
-rw-r--r-- | tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus | 7 | ||||
-rw-r--r-- | tools/memory-model/litmus-tests/README | 104 |
2 files changed, 105 insertions, 6 deletions
diff --git a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus index 0f749e419b34..094d58df7789 100644 --- a/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus +++ b/tools/memory-model/litmus-tests/ISA2+pooncelock+pooncelock+pombonce.litmus @@ -1,11 +1,10 @@ C ISA2+pooncelock+pooncelock+pombonce (* - * Result: Sometimes + * Result: Never * - * This test shows that the ordering provided by a lock-protected S - * litmus test (P0() and P1()) are not visible to external process P2(). - * This is likely to change soon. + * This test shows that write-write ordering provided by locks + * (in P0() and P1()) is visible to external process P2(). *) {} diff --git a/tools/memory-model/litmus-tests/README b/tools/memory-model/litmus-tests/README index 4581ec2d3c57..5ee08f129094 100644 --- a/tools/memory-model/litmus-tests/README +++ b/tools/memory-model/litmus-tests/README @@ -1,4 +1,6 @@ -This directory contains the following litmus tests: +============ +LITMUS TESTS +============ CoRR+poonceonce+Once.litmus Test of read-read coherence, that is, whether or not two @@ -36,7 +38,7 @@ IRIW+poonceonces+OnceOnce.litmus ISA2+pooncelock+pooncelock+pombonce.litmus Tests whether the ordering provided by a lock-protected S litmus test is visible to an external process whose accesses are - separated by smp_mb(). This addition of an external process to + separated by smp_mb(). This addition of an external process to S is otherwise known as ISA2. ISA2+poonceonces.litmus @@ -151,3 +153,101 @@ Z6.0+pooncerelease+poacquirerelease+fencembonceonce.litmus A great many more litmus tests are available here: https://github.com/paulmckrcu/litmus + +================== +LITMUS TEST NAMING +================== + +Litmus tests are usually named based on their contents, which means that +looking at the name tells you what the litmus test does. The naming +scheme covers litmus tests having a single cycle that passes through +each process exactly once, so litmus tests not fitting this description +are named on an ad-hoc basis. + +The structure of a litmus-test name is the litmus-test class, a plus +sign ("+"), and one string for each process, separated by plus signs. +The end of the name is ".litmus". + +The litmus-test classes may be found in the infamous test6.pdf: +https://www.cl.cam.ac.uk/~pes20/ppc-supplemental/test6.pdf +Each class defines the pattern of accesses and of the variables accessed. +For example, if the one process writes to a pair of variables, and +the other process reads from these same variables, the corresponding +litmus-test class is "MP" (message passing), which may be found on the +left-hand end of the second row of tests on page one of test6.pdf. + +The strings used to identify the actions carried out by each process are +complex due to a desire to have short(er) names. Thus, there is a tool to +generate these strings from a given litmus test's actions. For example, +consider the processes from SB+rfionceonce-poonceonces.litmus: + + P0(int *x, int *y) + { + int r1; + int r2; + + WRITE_ONCE(*x, 1); + r1 = READ_ONCE(*x); + r2 = READ_ONCE(*y); + } + + P1(int *x, int *y) + { + int r3; + int r4; + + WRITE_ONCE(*y, 1); + r3 = READ_ONCE(*y); + r4 = READ_ONCE(*x); + } + +The next step is to construct a space-separated list of descriptors, +interleaving descriptions of the relation between a pair of consecutive +accesses with descriptions of the second access in the pair. + +P0()'s WRITE_ONCE() is read by its first READ_ONCE(), which is a +reads-from link (rf) and internal to the P0() process. This is +"rfi", which is an abbreviation for "reads-from internal". Because +some of the tools string these abbreviations together with space +characters separating processes, the first character is capitalized, +resulting in "Rfi". + +P0()'s second access is a READ_ONCE(), as opposed to (for example) +smp_load_acquire(), so next is "Once". Thus far, we have "Rfi Once". + +P0()'s third access is also a READ_ONCE(), but to y rather than x. +This is related to P0()'s second access by program order ("po"), +to a different variable ("d"), and both accesses are reads ("RR"). +The resulting descriptor is "PodRR". Because P0()'s third access is +READ_ONCE(), we add another "Once" descriptor. + +A from-read ("fre") relation links P0()'s third to P1()'s first +access, and the resulting descriptor is "Fre". P1()'s first access is +WRITE_ONCE(), which as before gives the descriptor "Once". The string +thus far is thus "Rfi Once PodRR Once Fre Once". + +The remainder of P1() is similar to P0(), which means we add +"Rfi Once PodRR Once". Another fre links P1()'s last access to +P0()'s first access, which is WRITE_ONCE(), so we add "Fre Once". +The full string is thus: + + Rfi Once PodRR Once Fre Once Rfi Once PodRR Once Fre Once + +This string can be given to the "norm7" and "classify7" tools to +produce the name: + + $ norm7 -bell linux-kernel.bell \ + Rfi Once PodRR Once Fre Once Rfi Once PodRR Once Fre Once | \ + sed -e 's/:.*//g' + SB+rfionceonce-poonceonces + +Adding the ".litmus" suffix: SB+rfionceonce-poonceonces.litmus + +The descriptors that describe connections between consecutive accesses +within the cycle through a given litmus test can be provided by the herd +tool (Rfi, Po, Fre, and so on) or by the linux-kernel.bell file (Once, +Release, Acquire, and so on). + +To see the full list of descriptors, execute the following command: + + $ diyone7 -bell linux-kernel.bell -show edges |