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author | Jonathan Corbet <corbet@lwn.net> | 2016-08-07 15:09:14 -0600 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2016-08-18 17:39:24 -0600 |
commit | d228af5bcb60fda50f8b3a100c0539c4994df040 (patch) | |
tree | 3d204a825cc0a0555001140e165a7ba7ff11c0d6 /Documentation/sparse.txt | |
parent | 4b9033a33494ec9154d63e706e9e47f7eb3fd59e (diff) | |
download | linux-next-d228af5bcb60fda50f8b3a100c0539c4994df040.tar.gz |
docs: sphinxify sparse.txt and move to dev-tools
Fold the sparse document into the development tools set; no changes to the
text itself beyond formatting.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/sparse.txt')
-rw-r--r-- | Documentation/sparse.txt | 108 |
1 files changed, 0 insertions, 108 deletions
diff --git a/Documentation/sparse.txt b/Documentation/sparse.txt deleted file mode 100644 index eceab1308a8c..000000000000 --- a/Documentation/sparse.txt +++ /dev/null @@ -1,108 +0,0 @@ -Copyright 2004 Linus Torvalds -Copyright 2004 Pavel Machek <pavel@ucw.cz> -Copyright 2006 Bob Copeland <me@bobcopeland.com> - -Using sparse for typechecking -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -"__bitwise" is a type attribute, so you have to do something like this: - - typedef int __bitwise pm_request_t; - - enum pm_request { - PM_SUSPEND = (__force pm_request_t) 1, - PM_RESUME = (__force pm_request_t) 2 - }; - -which makes PM_SUSPEND and PM_RESUME "bitwise" integers (the "__force" is -there because sparse will complain about casting to/from a bitwise type, -but in this case we really _do_ want to force the conversion). And because -the enum values are all the same type, now "enum pm_request" will be that -type too. - -And with gcc, all the __bitwise/__force stuff goes away, and it all ends -up looking just like integers to gcc. - -Quite frankly, you don't need the enum there. The above all really just -boils down to one special "int __bitwise" type. - -So the simpler way is to just do - - typedef int __bitwise pm_request_t; - - #define PM_SUSPEND ((__force pm_request_t) 1) - #define PM_RESUME ((__force pm_request_t) 2) - -and you now have all the infrastructure needed for strict typechecking. - -One small note: the constant integer "0" is special. You can use a -constant zero as a bitwise integer type without sparse ever complaining. -This is because "bitwise" (as the name implies) was designed for making -sure that bitwise types don't get mixed up (little-endian vs big-endian -vs cpu-endian vs whatever), and there the constant "0" really _is_ -special. - -__bitwise__ - to be used for relatively compact stuff (gfp_t, etc.) that -is mostly warning-free and is supposed to stay that way. Warnings will -be generated without __CHECK_ENDIAN__. - -__bitwise - noisy stuff; in particular, __le*/__be* are that. We really -don't want to drown in noise unless we'd explicitly asked for it. - -Using sparse for lock checking -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -The following macros are undefined for gcc and defined during a sparse -run to use the "context" tracking feature of sparse, applied to -locking. These annotations tell sparse when a lock is held, with -regard to the annotated function's entry and exit. - -__must_hold - The specified lock is held on function entry and exit. - -__acquires - The specified lock is held on function exit, but not entry. - -__releases - The specified lock is held on function entry, but not exit. - -If the function enters and exits without the lock held, acquiring and -releasing the lock inside the function in a balanced way, no -annotation is needed. The tree annotations above are for cases where -sparse would otherwise report a context imbalance. - -Getting sparse -~~~~~~~~~~~~~~ - -You can get latest released versions from the Sparse homepage at -https://sparse.wiki.kernel.org/index.php/Main_Page - -Alternatively, you can get snapshots of the latest development version -of sparse using git to clone.. - - git://git.kernel.org/pub/scm/devel/sparse/sparse.git - -DaveJ has hourly generated tarballs of the git tree available at.. - - http://www.codemonkey.org.uk/projects/git-snapshots/sparse/ - - -Once you have it, just do - - make - make install - -as a regular user, and it will install sparse in your ~/bin directory. - -Using sparse -~~~~~~~~~~~~ - -Do a kernel make with "make C=1" to run sparse on all the C files that get -recompiled, or use "make C=2" to run sparse on the files whether they need to -be recompiled or not. The latter is a fast way to check the whole tree if you -have already built it. - -The optional make variable CF can be used to pass arguments to sparse. The -build system passes -Wbitwise to sparse automatically. To perform endianness -checks, you may define __CHECK_ENDIAN__: - - make C=2 CF="-D__CHECK_ENDIAN__" - -These checks are disabled by default as they generate a host of warnings. |