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Arm64 test #12

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@chantra chantra commented Oct 4, 2022

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Most Linux-kernel uses of locking are straightforward, but there are
corner-case uses that rely on less well-known aspects of the lock and
unlock primitives.  This commit therefore adds a locking.txt and litmus
tests in Documentation/litmus-tests/locking to explain these corner-case
uses.

Signed-off-by: Paul E. McKenney <[email protected]>
Currently, judgelitmus.sh treats timeouts (as in the "--timeout" argument)
as "!!! Verification error".  This can be misleading because it is quite
possible that running the test longer would have produced a verification.
This commit therefore changes judgelitmus.sh to check for timeouts and
to report them with "!!! Timeout".

Signed-off-by: Paul E. McKenney <[email protected]>
Currently, cmplitmushist.sh treats timeouts (as in the "--timeout"
argument) as "Missing Observation line".  This can be misleading because
it is quite possible that running the test longer would have produced
a verification.  This commit therefore changes cmplitmushist.sh to check
for timeouts and to report them with "Timed out".

Signed-off-by: Paul E. McKenney <[email protected]>
Currently, judgelitmus.sh treats use of unknown primitives (such as
srcu_read_lock() prior to SRCU support) as "!!! Verification error".
This can be misleading because it fails to call out typos and running
a version LKMM on a litmus test requiring a feature not provided by
that version.  This commit therefore changes judgelitmus.sh to check
for unknown primitives and to report them, for example, with:

	'!!! Current LKMM version does not know "rcu_write_lock"'.

Signed-off-by: Paul E. McKenney <[email protected]>
If a litmus test specifies "Result: Never" and if it contains an
unconditional ("hard") deadlock, then running checklitmus.sh on it will
not flag any errors, despite the fact that there are no executions.
This commit therefore updates judgelitmus.sh to complain about tests
with no executions that are marked, but not as "Result: DEADLOCK".

Signed-off-by: Paul E. McKenney <[email protected]>
This commit adds a --hw argument to parseargs.sh to specify the CPU
family for a hardware verification.  For example, "--hw AArch64" will
specify that a C-language litmus test is to be translated to ARMv8 and
the result verified.  This will set the LKMM_HW_MAP_FILE environment
variable accordingly.  If there is no --hw argument, this environment
variable will be set to the empty string.

Signed-off-by: Paul E. McKenney <[email protected]>
This commit makes the judgelitmus.sh script check the --hw argument
(AKA the LKMM_HW_MAP_FILE environment variable) and to adjust its
judgment for a run where a C-language litmus test has been translated to
assembly and the assembly version verified.  In this case, the assembly
verification output is checked against the C-language script's "Result:"
comment.  However, because hardware can be stronger than LKMM requires,
the judgelitmus.sh script forgives verification mismatches featuring
a "Sometimes" in the C-language script and an "Always" or "Never"
assembly-language verification.

Note that deadlock is not forgiven, however, this should not normally be
an issue given that C-language tests containing locking, RCU, or SRCU
cannot be translated to assembly.  However, this issue can crop up in
litmus tests that mimic deadlock by using the "filter" clause to ignore
all executions.  It can also crop up when certain herd arguments are
used to autofilter everything that does not match the "exists" clause
in cases where the "exists" clause cannot be satisfied.

Signed-off-by: Paul E. McKenney <[email protected]>
This commit abstracts out common function to check a given litmus test
for locking, RCU, and SRCU in order to avoid duplicating code.

Signed-off-by: Paul E. McKenney <[email protected]>
The checkalllitmus.sh runs litmus tests in the litmus-tests directory,
not those in the github archive, so this commit updates the comment to
reflect this reality.

Signed-off-by: Paul E. McKenney <[email protected]>
This commit makes checklitmus.sh and checkalllitmus.sh check to see
if a hardware verification was specified (via the --hw command-line
argument, which sets the LKMM_HW_MAP_FILE environment variable).
If so, the C-language litmus test is converted to the specified type
of assembly-language litmus test and herd is run on it.  Hardware is
permitted to be stronger than LKMM requires, so "Always" and "Never"
verifications of "Sometimes" C-language litmus tests are forgiven.

Signed-off-by: Paul E. McKenney <[email protected]>
The judgelitmus.sh script currently relies solely on the "Result:"
comment in the .litmus file.  This is problematic when using the --hw
argument, because it is necessary to check the hardware model against
LKMM even in the absence of "Result:" comments.

This commit therefore modifies judgelitmus.sh to check the observation
in a .litmus.out file, in case one was generated by a previous LKMM run.

Signed-off-by: Paul E. McKenney <[email protected]>
This commit prepares for adding --hw capability to github litmus-test
scripts by splitting runlitmus.sh (which simply runs the verification)
out of checklitmus.sh (which also judges the results).

Signed-off-by: Paul E. McKenney <[email protected]>
In the absence of "Result:" comments, the runlitmus.sh script relies on
litmus.out files from prior LKMM runs.  This can be a bit user-hostile,
so this commit makes runlitmus.sh generate any needed .litmus.out files
that don't already exist.

Signed-off-by: Paul E. McKenney <[email protected]>
When the github scripts see ".litmus.out", they assume that there must be
a corresponding C-language ".litmus" file.  Won't they be disappointed
when they instead see nothing, or, worse yet, the corresponding
assembly-language litmus test?  This commit therefore swaps the hardware
tag with the "litmus" to avoid this sort of disappointment.

This commit also adjusts the .gitignore file so as to avoid adding these
new ".out" files to git.

[ paulmck: Apply Akira Yokosawa feedback. ]
Signed-off-by: Paul E. McKenney <[email protected]>
This commit retains the assembly-language litmus tests generated from
the C-language litmus tests, appending the hardware tag to the original
C-language litmus test's filename.  Thus, S+poonceonces.litmus.AArch64
contains the Armv8 assembly language corresponding to the C-language
S+poonceonces.litmus test.

This commit also updates the .gitignore to avoid committing these
automatically generated assembly-language litmus tests.

Signed-off-by: Paul E. McKenney <[email protected]>
Currently, the scripts specify the CPU's .cat file to herd.  But this is
pointless because herd will select a good and sufficient .cat file from
the assembly-language litmus test itself.  This commit therefore removes
the -model argument to herd, allowing herd to figure the CPU family out
itself.

Note that the user can override herd's choice using the "--herdopts"
argument to the scripts.

Suggested-by: Luc Maranget <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
It turns out that the jingle7 tool is currently a bit picky about
the litmus tests it is willing to process.  This commit therefore
ensures that jingle7 failures are reported.

Signed-off-by: Paul E. McKenney <[email protected]>
Adding the -v flag to jingle7 invocations gives much useful information
on why jingle7 didn't like a given litmus test.  This commit therefore
adds this flag and saves off any such information into a .err file.

Suggested-by: Luc Maranget <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
This commits enables the "--hw" argument for the checkghlitmus.sh script,
causing it to convert any applicable C-language litmus tests to the
specified flavor of assembly language, to verify these assembly-language
litmus tests, and checking compatibility of the outcomes.

Note that the conversion does not yet handle locking, RCU, SRCU, plain
C-language memory accesses, or casts.

Signed-off-by: Paul E. McKenney <[email protected]>
The parseargs.sh regular expression for the --jobs argument incorrectly
requires that the number of jobs be at least 10, that is, have at least
two digits.  This commit therefore adjusts this regular expression to
allow single-digit numbers of jobs to be specified.

Signed-off-by: Paul E. McKenney <[email protected]>
The checkghlitmus.sh script currently uses grep to ignore non-C-language
litmus tests, which is a bit fragile.  This commit therefore enlists the
aid of "mselect7 -arch C", given Luc Maraget's recent modifications that
allow mselect7 to operate in filter mode.

This change requires herdtools 7.52-32-g1da3e0e50977 or later.

Signed-off-by: Paul E. McKenney <[email protected]>
The history-check scripts currently use grep to ignore non-C-language
litmus tests, which is a bit fragile.  This commit therefore enlists the
aid of "mselect7 -arch C", given Luc Maraget's recent modifications that
allow mselect7 to operate in filter mode.

This change requires herdtools 7.52-32-g1da3e0e50977 or later.

Signed-off-by: Paul E. McKenney <[email protected]>
Currently, parseargs.sh expects to consume all the command-line arguments,
which prevents the calling script from having any of its own arguments.
This commit therefore causes parseargs.sh to stop consuming arguments
when it encounters a "--" argument, leaving any remaining arguments for
the calling script.

Signed-off-by: Paul E. McKenney <[email protected]>
…ests

This commit adds a checktheselitmus.sh script that runs the litmus tests
specified on the command line.  This is useful for verifying fixes to
specific litmus tests.

Signed-off-by: Paul E. McKenney <[email protected]>
This commit adds functionality to judgelitmus.sh to allow it to handle
both the "DATARACE" markers in the "Result:" comments in litmus tests
and the "Flag data-race" markers in LKMM output.  For C-language tests,
if either marker is present, the other must also be as well, at least for
litmus tests having a "Result:" comment.  If the LKMM output indicates
a data race, then failures of the Always/Sometimes/Never portion of the
"Result:" prediction are forgiven.

The reason for forgiving "Result:" mispredictions is that data races can
result in "interesting" compiler optimizations, so that all bets are off
in the data-race case.

[ paulmck: Apply Akira Yokosawa feedback. ]
Signed-off-by: Paul E. McKenney <[email protected]>
The scripts that generate the litmus tests in the "auto" directory of
the https://github.com/paulmckrcu/litmus archive place the "Result:"
tag into a single-line ocaml comment, which judgelitmus.sh currently
does not recognize.  This commit therefore makes judgelitmus.sh
recognize both the multiline comment format that it currently does
and the automatically generated single-line format.

Signed-off-by: Paul E. McKenney <[email protected]>
Litmus tests involving atomic operations produce LL/SC loops on a number
of architectures, and unrolling these loops can result in excessive
verification times or even stack overflows.  This commit therefore uses
the "-unroll 0" herd7 argument to avoid unrolling, on the grounds that
additional passes through an LL/SC loop should not change the verification.

Note however, that certain bugs in the mapping of the LL/SC loop to
machine instructions may go undetected.  On the other hand, herd7 might
not be the best vehicle for finding such bugs in any case.  (You do
stress-test your architecture-specific code, don't you?)

Suggested-by: Luc Maranget <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
nolibc.2022.08.31b: nolibc updates
@kernel-patches-bot kernel-patches-bot force-pushed the rcu-dev_test branch 30 times, most recently from 4169cae to f25b394 Compare October 20, 2022 16:39
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