percpu-refcount was incorrectly using preempt_disable/enable() for RCU
critical sections against call_rcu(). 6a24474da8 ("percpu-refcount:
consistently use plain (non-sched) RCU") fixed it by converting the
preepmtion operations with rcu_read_[un]lock() citing that there isn't
any advantage in using sched-RCU over using the usual one; however,
rcu_read_[un]lock() for the preemptible RCU implementation -
CONFIG_TREE_PREEMPT_RCU, chosen when CONFIG_PREEMPT - are slightly
more expensive than preempt_disable/enable().
In a contrived microbench which repeats the followings,
- percpu_ref_get()
- copy 32 bytes of data into percpu buffer
- percpu_put_get()
- copy 32 bytes of data into percpu buffer
rcu_read_[un]lock() used in percpu_ref_get/put() makes it go slower by
about 15% when compared to using sched-RCU.
As the RCU critical sections are extremely short, using sched-RCU
shouldn't have any latency implications. Convert to RCU-sched.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Kent Overstreet <koverstreet@google.com>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Implement percpu_tryget() which stops giving out references once the
percpu_ref is visible as killed. Because the refcnt is per-cpu,
different CPUs will start to see a refcnt as killed at different
points in time and tryget() may continue to succeed on subset of cpus
for a while after percpu_ref_kill() returns.
For use cases where it's necessary to know when all CPUs start to see
the refcnt as dead, percpu_ref_kill_and_confirm() is added. The new
function takes an extra argument @confirm_kill which is invoked when
the refcnt is guaranteed to be viewed as killed on all CPUs.
While this isn't the prettiest interface, it doesn't force synchronous
wait and is much safer than requiring the caller to do its own
call_rcu().
v2: Patch description rephrased to emphasize that tryget() may
continue to succeed on some CPUs after kill() returns as suggested
by Kent.
v3: Function comment in percpu_ref_kill_and_confirm() updated warning
people to not depend on the implied RCU grace period from the
confirm callback as it's an implementation detail.
Signed-off-by: Tejun Heo <tj@kernel.org>
Slightly-Grumpily-Acked-by: Kent Overstreet <koverstreet@google.com>
Normally, percpu_ref_init() initializes and percpu_ref_kill()
initiates destruction which completes asynchronously. The
asynchronous destruction can be problematic in init failure path where
the caller wants to destroy half-constructed object - distinguishing
half-constructed objects from the usual release method can be painful
for complex objects.
This patch implements percpu_ref_cancel_init() which synchronously
destroys the percpu_ref without invoking release. To avoid
unintentional misuses, the function requires the ref to have finished
percpu_ref_init() but never used and triggers WARN otherwise.
v2: Explain the weird name and usage restriction in the function
comment.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Kent Overstreet <koverstreet@google.com>
Two small changes.
* Unlike most init functions, percpu_ref_init() allocates memory and
may fail. Let's mark it with __must_check in case the caller
forgets.
* percpu_ref_kill_rcu() is unnecessarily using ACCESS_ONCE() to
dereference @ref->pcpu_count, which can be misleading. The pointer
is guaranteed to be valid and visible and can't change underneath
the function. Drop ACCESS_ONCE().
Signed-off-by: Tejun Heo <tj@kernel.org>
* s/percpu_ref_release/percpu_ref_func_t/ as it's customary to have _t
postfix for types and the type is gonna be used for a different type
of callback too.
* Add @ARG to function comments.
* Drop unnecessary and unaligned indentation from percpu_ref_init()
function comment.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Kent Overstreet <koverstreet@google.com>
Unlike kobject_set_name(), the kset_create_and_add() interface does not
provide a way to use format strings, so make sure that the interface
cannot be abused accidentally. It looks like all current callers use
static strings, so there's no existing flaw.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Since we have at least one user of this function outside of CONFIG_NET
scope, we have to provide this function independently. The proposed
solution is to move it under lib/net_utils.c with corresponding
configuration variable and select wherever it is needed.
Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
lib/crc-t10dif.c:42:1-3: WARNING: PTR_RET can be used
Use PTR_RET rather than if(IS_ERR(...)) + PTR_ERR
Generated by: coccinelle/api/ptr_ret.cocci
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The cmpxchg() was just to ensure the debug check didn't race, which was
a bit excessive. The caller is supposed to do the appropriate
synchronization, which means percpu_ref_kill() can just do a simple
store.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This implements a refcount with similar semantics to
atomic_get()/atomic_dec_and_test() - but percpu.
It also implements two stage shutdown, as we need it to tear down the
percpu counts. Before dropping the initial refcount, you must call
percpu_ref_kill(); this puts the refcount in "shutting down mode" and
switches back to a single atomic refcount with the appropriate
barriers (synchronize_rcu()).
It's also legal to call percpu_ref_kill() multiple times - it only
returns true once, so callers don't have to reimplement shutdown
synchronization.
[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: coding-style tweak]
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Tejun Heo <tj@kernel.org>
The umul_ppmm() macro for parisc uses the xmpyu assembler statement
which does calculation via a floating point register.
But usage of floating point registers inside the Linux kernel are not
allowed and gcc will stop compilation due to the -mdisable-fpregs
compiler option.
Fix this by disabling the umul_ppmm() and udiv_qrnnd() macros. The
mpilib will then use the generic built-in implementations instead.
Signed-off-by: Helge Deller <deller@gmx.de>
Pull driver core fixes from Greg Kroah-Hartman:
"Here are 3 tiny driver core fixes for 3.10-rc2.
A needed symbol export, a change to make it easier to track down
offending sysfs files with incorrect attributes, and a klist bugfix.
All have been in linux-next for a while"
* tag 'driver-core-3.10-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
klist: del waiter from klist_remove_waiters before wakeup waitting process
driver core: print sysfs attribute name when warning about bogus permissions
driver core: export subsys_virtual_register
There is a race between klist_remove and klist_release. klist_remove
uses a local var waiter saved on stack. When klist_release calls
wake_up_process(waiter->process) to wake up the waiter, waiter might run
immediately and reuse the stack. Then, klist_release calls
list_del(&waiter->list) to change previous
wait data and cause prior waiter thread corrupt.
The patch fixes it against kernel 3.9.
Signed-off-by: wang, biao <biao.wang@intel.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When CRC T10 DIF is calculated using the crypto transform framework, we
wrap the crc_t10dif function call to utilize it. This allows us to
take advantage of any accelerated CRC T10 DIF transform that is
plugged into the crypto framework.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
ERROR: "memcpy_fromiovec" [drivers/vhost/vhost_scsi.ko] undefined!
That function is only present with CONFIG_NET. Turns out that
crypto/algif_skcipher.c also uses that outside net, but it actually
needs sockets anyway.
In addition, commit 6d4f0139d6 added
CONFIG_NET dependency to CONFIG_VMCI for memcpy_toiovec, so hoist
that function and revert that commit too.
socket.h already includes uio.h, so no callers need updating; trying
only broke things fo x86_64 randconfig (thanks Fengguang!).
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Pull block driver updates from Jens Axboe:
"It might look big in volume, but when categorized, not a lot of
drivers are touched. The pull request contains:
- mtip32xx fixes from Micron.
- A slew of drbd updates, this time in a nicer series.
- bcache, a flash/ssd caching framework from Kent.
- Fixes for cciss"
* 'for-3.10/drivers' of git://git.kernel.dk/linux-block: (66 commits)
bcache: Use bd_link_disk_holder()
bcache: Allocator cleanup/fixes
cciss: bug fix to prevent cciss from loading in kdump crash kernel
cciss: add cciss_allow_hpsa module parameter
drivers/block/mg_disk.c: add CONFIG_PM_SLEEP to suspend/resume functions
mtip32xx: Workaround for unaligned writes
bcache: Make sure blocksize isn't smaller than device blocksize
bcache: Fix merge_bvec_fn usage for when it modifies the bvm
bcache: Correctly check against BIO_MAX_PAGES
bcache: Hack around stuff that clones up to bi_max_vecs
bcache: Set ra_pages based on backing device's ra_pages
bcache: Take data offset from the bdev superblock.
mtip32xx: mtip32xx: Disable TRIM support
mtip32xx: fix a smatch warning
bcache: Disable broken btree fuzz tester
bcache: Fix a format string overflow
bcache: Fix a minor memory leak on device teardown
bcache: Documentation updates
bcache: Use WARN_ONCE() instead of __WARN()
bcache: Add missing #include <linux/prefetch.h>
...
- make warning smp-safe
- result of atomic _unless_zero functions should be checked by caller
to avoid use-after-free error
- trivial whitespace fix.
Link: https://lkml.org/lkml/2013/4/12/391
Tested: compile x86, boot machine and run xfstests
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
[ Removed line-break, changed to use WARN_ON_ONCE() - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge rwsem optimizations from Michel Lespinasse:
"These patches extend Alex Shi's work (which added write lock stealing
on the rwsem slow path) in order to provide rwsem write lock stealing
on the fast path (that is, without taking the rwsem's wait_lock).
I have unfortunately been unable to push this through -next before due
to Ingo Molnar / David Howells / Peter Zijlstra being busy with other
things. However, this has gotten some attention from Rik van Riel and
Davidlohr Bueso who both commented that they felt this was ready for
v3.10, and Ingo Molnar has said that he was OK with me pushing
directly to you. So, here goes :)
Davidlohr got the following test results from pgbench running on a
quad-core laptop:
| db_size | clients | tps-vanilla | tps-rwsem |
+---------+----------+----------------+--------------+
| 160 MB | 1 | 5803 | 6906 | + 19.0%
| 160 MB | 2 | 13092 | 15931 |
| 160 MB | 4 | 29412 | 33021 |
| 160 MB | 8 | 32448 | 34626 |
| 160 MB | 16 | 32758 | 33098 |
| 160 MB | 20 | 26940 | 31343 | + 16.3%
| 160 MB | 30 | 25147 | 28961 |
| 160 MB | 40 | 25484 | 26902 |
| 160 MB | 50 | 24528 | 25760 |
------------------------------------------------------
| 1.6 GB | 1 | 5733 | 7729 | + 34.8%
| 1.6 GB | 2 | 9411 | 19009 | + 101.9%
| 1.6 GB | 4 | 31818 | 33185 |
| 1.6 GB | 8 | 33700 | 34550 |
| 1.6 GB | 16 | 32751 | 33079 |
| 1.6 GB | 20 | 30919 | 31494 |
| 1.6 GB | 30 | 28540 | 28535 |
| 1.6 GB | 40 | 26380 | 27054 |
| 1.6 GB | 50 | 25241 | 25591 |
------------------------------------------------------
| 7.6 GB | 1 | 5779 | 6224 |
| 7.6 GB | 2 | 10897 | 13611 | + 24.9%
| 7.6 GB | 4 | 32683 | 33108 |
| 7.6 GB | 8 | 33968 | 34712 |
| 7.6 GB | 16 | 32287 | 32895 |
| 7.6 GB | 20 | 27770 | 31689 | + 14.1%
| 7.6 GB | 30 | 26739 | 29003 |
| 7.6 GB | 40 | 24901 | 26683 |
| 7.6 GB | 50 | 17115 | 25925 | + 51.5%
------------------------------------------------------
(Davidlohr also has one additional patch which further improves
throughput, though I will ask him to send it directly to you as I have
suggested some minor changes)."
* emailed patches from Michel Lespinasse <walken@google.com>:
rwsem: no need for explicit signed longs
x86 rwsem: avoid taking slow path when stealing write lock
rwsem: do not block readers at head of queue if other readers are active
rwsem: implement support for write lock stealing on the fastpath
rwsem: simplify __rwsem_do_wake
rwsem: skip initial trylock in rwsem_down_write_failed
rwsem: avoid taking wait_lock in rwsem_down_write_failed
rwsem: use cmpxchg for trying to steal write lock
rwsem: more agressive lock stealing in rwsem_down_write_failed
rwsem: simplify rwsem_down_write_failed
rwsem: simplify rwsem_down_read_failed
rwsem: move rwsem_down_failed_common code into rwsem_down_{read,write}_failed
rwsem: shorter spinlocked section in rwsem_down_failed_common()
rwsem: make the waiter type an enumeration rather than a bitmask
Greg Kroah-Hartman
Tejun Heo
Chen Gang
Kees Cook
Andy Shevchenko
Herbert Xu
Kent Overstreet
Seth Jennings
Steven Rostedt
Helge Deller
Linus Torvalds
Randy Dunlap
wang, biao
Tim Chen
Rusty Russell
Davidlohr Bueso
Anatol Pomozov