Messages in this thread | | | From | Tejun Heo <> | Subject | [PATCHSET v2] percpu_ref, RCU: Audit RCU usages in percpu_ref users | Date | Wed, 14 Mar 2018 12:41:57 -0700 |
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Hello,
Linus, if you want to pick up the first three fix patches, please pull from the following branch.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git percpu_ref-rcu-audit-fixes
Changes from v1[L] are
* blk_queue_enter() patch dropped. Needs further investigation.
* queue_rcu_work_on() dropped and documentation improved.
* rcu_work conversion patches separated out.
Original patchset description follows.
Jann Horn found that aio was depending on the internal RCU grace periods of percpu-ref and that it's broken because aio uses regular RCU while percpu_ref uses sched-RCU.
Depending on percpu_ref's internal grace periods isn't a good idea because
* The RCU type might not match.
* percpu_ref's grace periods are used to switch to atomic mode. They aren't between the last put and the invocation of the last release. This is easy to get confused about and can lead to subtle bugs.
* percpu_ref might not have grace periods at all depending on its current operation mode.
This patchset audits all percpu_ref users for their RCU usages, clarifies percpu_ref documentation that the internal grace periods must not be depended upon, and introduces rcu_work to simplify bouncing to a workqueue after an RCU grace period.
This patchset contains the following eight patches.
0001-fs-aio-Add-explicit-RCU-grace-period-when-freeing-ki.patch 0002-fs-aio-Use-RCU-accessors-for-kioctx_table-table.patch 0003-RDMAVT-Fix-synchronization-around-percpu_ref.patch 0004-HMM-Remove-superflous-RCU-protection-around-radix-tr.patch 0005-percpu_ref-Update-doc-to-dissuade-users-from-dependi.patch 0006-RCU-workqueue-Implement-rcu_work.patch 0007-cgroup-Use-rcu_work-instead-of-explicit-rcu-and-work.patch 0008-fs-aio-Use-rcu_work-instead-of-explicit-rcu-and-work.patch
0001-0003 are fixes and tagged -stable.
0004 removes (seemingly) superflous RCU read lock usages.
0005 updates the doc and 0006-0008 introduce rcu_work and use it instead of open-coded rcu+work.
This patchset is also available in the following git tree.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git percpu_ref-rcu-audit-v2
diffstat follows. Thanks.
drivers/infiniband/sw/rdmavt/mr.c | 10 ++++--- fs/aio.c | 39 ++++++++++++++++----------- include/linux/cgroup-defs.h | 2 - include/linux/percpu-refcount.h | 18 ++++++++---- include/linux/workqueue.h | 23 ++++++++++++++++ kernel/cgroup/cgroup.c | 21 ++++---------- kernel/workqueue.c | 54 ++++++++++++++++++++++++++++++++++++++ lib/percpu-refcount.c | 2 + mm/hmm.c | 12 +------- 9 files changed, 130 insertions(+), 51 deletions(-)
-- tejun
[L] http://lkml.kernel.org/r/20180306172657.3060270-1-tj@kernel.org http://lkml.kernel.org/r/20180306173316.3088458-1-tj@kernel.org
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