linux-toradex.git/lib/percpu-refcount.c, branch v5.12-rc6

percpu_ref: Dump mem_dump_obj() info upon reference-count underflow

2021-01-22T23:24:23+00:00

Reference-count underflow for percpu_ref is detected in the RCU callback
percpu_ref_switch_to_atomic_rcu(), and the resulting warning does not
print anything allowing easy identification of which percpu_ref use
case is underflowing.  This is of course not normally a problem when
developing a new percpu_ref use case because it is most likely that
the problem resides in this new use case.  However, when deploying a
new kernel to a large set of servers, the underflow might well be a new
corner case in any of the old percpu_ref use cases.

This commit therefore calls mem_dump_obj() to dump out any additional
available information on the underflowing percpu_ref instance.

Cc: Ming Lei 
Cc: Jens Axboe 
Cc: Joonsoo Kim 
Reported-by: Andrii Nakryiko 
Tested-by: Naresh Kamboju 
Signed-off-by: Paul E. McKenney

percpu_ref: don't refer to ref->data if it isn't allocated

2020-10-09T18:32:06+00:00

We can't check ref->data->confirm_switch directly in __percpu_ref_exit(), since
ref->data may not be allocated in one not-initialized refcount.

Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
Reported-by: syzbot+fd15ff734dace9e16437@syzkaller.appspotmail.com
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe

percpu_ref: reduce memory footprint of percpu_ref in fast path

2020-10-06T13:29:36+00:00

'struct percpu_ref' is often embedded into one user structure, and the
instance is usually referenced in fast path, however actually only
'percpu_count_ptr' is needed in fast path.

So move other fields into one new structure of 'percpu_ref_data', and
allocate it dynamically via kzalloc(), then memory footprint of
'percpu_ref' in fast path is reduced a lot and becomes suitable to put
into hot cacheline of user structure.

Signed-off-by: Ming Lei 
Tested-by: Veronika Kabatova 
Reviewed-by: Christoph Hellwig 
Acked-by: Tejun Heo 
Cc: Sagi Grimberg 
Cc: Tejun Heo 
Cc: Christoph Hellwig 
Cc: Jens Axboe 
Cc: Bart Van Assche 
Signed-off-by: Jens Axboe

lib/percpu-refcount.c: use a more common logging style

2020-06-05T02:06:25+00:00

Remove the trailing newline from the used-once pr_fmt and add it to the
single use of pr_ in this code to use a more common logging style.

Miscellanea:

o Use %lu in the pr_debug format and remove the unnecessary cast

Signed-off-by: Joe Perches 
Signed-off-by: Andrew Morton 
Cc: Christophe JAILLET 
Link: http://lkml.kernel.org/r/47372467902a047c03b0fd29aab56e0c38d3f848.camel@perches.com
Signed-off-by: Linus Torvalds

percpu_ref: Fix comment regarding percpu_ref_init flags

2020-03-05T21:10:26+00:00

The comment for percpu_ref_init() implies that using
PERCPU_REF_ALLOW_REINIT will cause the refcount to start at 0.  But
this is not true.  PERCPU_REF_ALLOW_REINIT starts the count at 1 as
if the flags were zero.  Add this fact to the kernel doc comment.

Signed-off-by: Ira Weiny 
[Dennis: reworded]
Signed-off-by: Dennis Zhou

Merge branch 'for-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu

2019-07-14T23:17:18+00:00

Pull percpu updates from Dennis Zhou:
 "This includes changes to let percpu_ref release the backing percpu
  memory earlier after it has been switched to atomic in cases where the
  percpu ref is not revived.

  This will help recycle percpu memory earlier in cases where the
  refcounts are pinned for prolonged periods of time"

* 'for-5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu:
  percpu_ref: release percpu memory early without PERCPU_REF_ALLOW_REINIT
  md: initialize percpu refcounters using PERCU_REF_ALLOW_REINIT
  io_uring: initialize percpu refcounters using PERCU_REF_ALLOW_REINIT
  percpu_ref: introduce PERCPU_REF_ALLOW_REINIT flag

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

percpu_ref: release percpu memory early without PERCPU_REF_ALLOW_REINIT

2019-05-09T17:51:06+00:00

Release percpu memory after finishing the switch to the atomic mode
if only PERCPU_REF_ALLOW_REINIT isn't set.

Signed-off-by: Roman Gushchin 
Acked-by: Tejun Heo 
Signed-off-by: Dennis Zhou

treewide: Switch printk users from %pf and %pF to %ps and %pS, respectively

2019-04-09T12:19:06+00:00

%pF and %pf are functionally equivalent to %pS and %ps conversion
specifiers. The former are deprecated, therefore switch the current users
to use the preferred variant.

The changes have been produced by the following command:

	git grep -l '%p[fF]' | grep -v '^\(tools\|Documentation\)/' | \
	while read i; do perl -i -pe 's/%pf/%ps/g; s/%pF/%pS/g;' $i; done

And verifying the result.

Link: http://lkml.kernel.org/r/20190325193229.23390-1-sakari.ailus@linux.intel.com
Cc: Andy Shevchenko 
Cc: linux-arm-kernel@lists.infradead.org
Cc: sparclinux@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: xen-devel@lists.xenproject.org
Cc: linux-acpi@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: drbd-dev@lists.linbit.com
Cc: linux-block@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Cc: linux-nvdimm@lists.01.org
Cc: linux-pci@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: linux-btrfs@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: linux-mm@kvack.org
Cc: ceph-devel@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Sakari Ailus 
Acked-by: David Sterba  (for btrfs)
Acked-by: Mike Rapoport  (for mm/memblock.c)
Acked-by: Bjorn Helgaas  (for drivers/pci)
Acked-by: Rafael J. Wysocki 
Signed-off-by: Petr Mladek

percpu-refcount: Replace call_rcu_sched() with call_rcu()

2018-11-27T17:21:45+00:00

Now that call_rcu()'s callback is not invoked until after all
preempt-disable regions of code have completed (in addition to explicitly
marked RCU read-side critical sections), call_rcu() can be used in place
of call_rcu_sched().  This commit therefore makes that change.

Signed-off-by: Paul E. McKenney 
Cc: Ming Lei 
Cc: Bart Van Assche 
Cc: Jens Axboe 
Acked-by: Tejun Heo