Commit Graph

7 Commits

Author SHA1 Message Date
NeilBrown
db1afffab0 kref: remove kref_set
Of the three uses of kref_set in the kernel:

 One really should be kref_put as the code is letting go of a
    reference,
 Two really should be kref_init because the kref is being
    initialised.

This suggests that making kref_set available encourages bad code.
So fix the three uses and remove kref_set completely.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-05-21 09:37:29 -07:00
Tejun Heo
5a0e3ad6af include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-30 22:02:32 +09:00
Evgeniy Polyakov
41ca28ab2a kref: add kref_set()
This adds kref_set() to the kref api for future use by people who really
know what they are doing with krefs...

From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2008-01-24 20:40:05 -08:00
Oliver Neukum
1b0b3b9980 kref: fix CPU ordering with respect to krefs
some atomic operations are only atomic, not ordered. Thus a CPU is allowed
to reorder memory references to an object to before the reference is
obtained. This fixes it.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2007-04-27 10:57:29 -07:00
Venkatesh Pallipadi
f334b60b43 kref refcnt and false positives
With WARN_ON addition to kobject_init()
[ http://kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.19/2.6.19-mm1/dont-use/broken-out/gregkh-driver-kobject-warn.patch ]

I started seeing following WARNING on CPU offline followed by online on my
x86_64 system.

WARNING at lib/kobject.c:172 kobject_init()

Call Trace:
 [<ffffffff8020ab45>] dump_trace+0xaa/0x3ef
 [<ffffffff8020aec4>] show_trace+0x3a/0x50
 [<ffffffff8020b0f6>] dump_stack+0x15/0x17
 [<ffffffff80350abc>] kobject_init+0x3f/0x8a
 [<ffffffff80350be1>] kobject_register+0x1a/0x3e
 [<ffffffff803bbd89>] sysdev_register+0x5b/0xf9
 [<ffffffff80211d0b>] mce_create_device+0x77/0xf4
 [<ffffffff80211dc2>] mce_cpu_callback+0x3a/0xe5
 [<ffffffff805632fd>] notifier_call_chain+0x26/0x3b
 [<ffffffff8023f6f3>] raw_notifier_call_chain+0x9/0xb
 [<ffffffff802519bf>] _cpu_up+0xb4/0xdc
 [<ffffffff80251a12>] cpu_up+0x2b/0x42
 [<ffffffff803bef00>] store_online+0x4a/0x72
 [<ffffffff803bb6ce>] sysdev_store+0x24/0x26
 [<ffffffff802baaa2>] sysfs_write_file+0xcf/0xfc
 [<ffffffff8027fc6f>] vfs_write+0xae/0x154
 [<ffffffff80280418>] sys_write+0x47/0x6f
 [<ffffffff8020963e>] system_call+0x7e/0x83
DWARF2 unwinder stuck at system_call+0x7e/0x83
Leftover inexact backtrace:

This is a false positive as mce.c is unregistering/registering sysfs
interfaces cleanly on hotplug.

kref_put() and conditional decrement of refcnt seems to be the root cause
for this and the patch below resolves the issue for me.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-12-20 10:56:43 -08:00
Eric Dumazet
8b5536bbee [PATCH] kref: avoid an atomic operation in kref_put()
Avoid an atomic operation in kref_put() when the last reference is
dropped. On most platforms, atomic_read() is a plan read of the counter
and involves no atomic at all.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2006-03-20 13:42:57 -08:00
Linus Torvalds
1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00