summaryrefslogtreecommitdiffstats
path: root/kernel/Documentation/sparse.txt
diff options
context:
space:
mode:
authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/Documentation/sparse.txt
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/Documentation/sparse.txt')
-rw-r--r--kernel/Documentation/sparse.txt108
1 files changed, 108 insertions, 0 deletions
diff --git a/kernel/Documentation/sparse.txt b/kernel/Documentation/sparse.txt
new file mode 100644
index 000000000..eceab1308
--- /dev/null
+++ b/kernel/Documentation/sparse.txt
@@ -0,0 +1,108 @@
+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.