linux-toradex.git/fs/eventfd.c, branch v2.6.34

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

2010-03-30T13:02:32+00:00

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 
Guess-its-ok-by: Christoph Lameter 
Cc: Ingo Molnar 
Cc: Lee Schermerhorn

eventfd - allow atomic read and waitqueue remove

2010-01-25T14:26:38+00:00

KVM needs a wait to atomically remove themselves from the eventfd ->poll()
wait queue head, in order to handle correctly their IRQfd deassign
operation.

This patch introduces such API, plus a way to read an eventfd from its
context.

Signed-off-by: Davide Libenzi 
Signed-off-by: Avi Kivity

anonfd: Allow making anon files read-only

2009-12-22T17:27:34+00:00

It seems a couple places such as arch/ia64/kernel/perfmon.c and
drivers/infiniband/core/uverbs_main.c could use anon_inode_getfile()
instead of a private pseudo-fs + alloc_file(), if only there were a way
to get a read-only file.  So provide this by having anon_inode_getfile()
create a read-only file if we pass O_RDONLY in flags.

Signed-off-by: Roland Dreier 
Signed-off-by: Al Viro

anonfd: split interface into file creation and install

2009-09-23T14:39:29+00:00

Split the anonfd interface into a bare file pointer creation one, and a
file pointer creation plus install one.

There are cases, like the usage of eventfds inside other kernel
interfaces, where the file pointer created by anonfd needs to be used
inside the initialization of other structures.

As it is right now, as soon as anon_inode_getfd() returns, the kenrle can
race with userspace closing the newly installed file descriptor.

This patch, while keeping the old anon_inode_getfd(), introduces a new
anon_inode_getfile() (whose services are reused in anon_inode_getfd())
that allows to split the file creation phase and the fd install one.

Once all the kernel structures are initialized, the code can call the
proper fd_install().

Gregory manifested the need for something like this inside KVM.

Signed-off-by: Davide Libenzi 
Cc: Alexander Viro 
Cc: James Morris 
Cc: Peter Zijlstra 
Cc: Gregory Haskins 
Acked-by: Serge Hallyn 
Acked-by: Roland Dreier 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

eventfd: revised interface and cleanups

2009-07-01T01:55:58+00:00

Change the eventfd interface to de-couple the eventfd memory context, from
the file pointer instance.

Without such change, there is no clean way to racely free handle the
POLLHUP event sent when the last instance of the file* goes away.  Also,
now the internal eventfd APIs are using the eventfd context instead of the
file*.

This patch is required by KVM's IRQfd code, which is still under
development.

Signed-off-by: Davide Libenzi 
Cc: Gregory Haskins 
Cc: Rusty Russell 
Cc: Benjamin LaHaise 
Cc: Avi Kivity 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

eventfd: export eventfd_signal and eventfd_fget for lguest

2009-06-12T12:57:09+00:00

lguest wants to attach eventfds to guest notifications, and lguest is
usually a module.

Signed-off-by: Rusty Russell 
To: Davide Libenzi

epoll keyed wakeups: make eventfd use keyed wakeups

2009-04-01T15:59:20+00:00

Introduce keyed event wakeups inside the eventfd code.

Signed-off-by: Davide Libenzi 
Cc: Alan Cox 
Cc: Ingo Molnar 
Cc: David Miller 
Cc: William Lee Irwin III 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

eventfd: improve support for semaphore-like behavior

2009-04-01T15:59:20+00:00

People started using eventfd in a semaphore-like way where before they
were using pipes.

That is, counter-based resource access.  Where a "wait()" returns
immediately by decrementing the counter by one, if counter is greater than
zero.  Otherwise will wait.  And where a "post(count)" will add count to
the counter releasing the appropriate amount of waiters.  If eventfd the
"post" (write) part is fine, while the "wait" (read) does not dequeue 1,
but the whole counter value.

The problem with eventfd is that a read() on the fd returns and wipes the
whole counter, making the use of it as semaphore a little bit more
cumbersome.  You can do a read() followed by a write() of COUNTER-1, but
IMO it's pretty easy and cheap to make this work w/out extra steps.  This
patch introduces a new eventfd flag that tells eventfd to only dequeue 1
from the counter, allowing simple read/write to make it behave like a
semaphore.  Simple test here:

http://www.xmailserver.org/eventfd-sem.c

To be back-compatible with earlier kernels, userspace applications should
probe for the availability of this feature via

#ifdef EFD_SEMAPHORE
	fd = eventfd2 (CNT, EFD_SEMAPHORE);
	if (fd == -1 && errno == EINVAL)
		
#else
		
#endif

Signed-off-by: Davide Libenzi 
Cc: 
Tested-by: Michael Kerrisk 
Cc: Ulrich Drepper 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[CVE-2009-0029] System call wrappers part 32

2009-01-14T13:15:31+00:00

Signed-off-by: Heiko Carstens

flag parameters: check magic constants

2008-07-24T17:47:29+00:00

This patch adds test that ensure the boundary conditions for the various
constants introduced in the previous patches is met.  No code is generated.

[akpm@linux-foundation.org: fix alpha]
Signed-off-by: Ulrich Drepper 
Acked-by: Davide Libenzi 
Cc: Michael Kerrisk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds