linux-toradex.git/kernel/rcu/srcutree.c, branch v5.9-rc5 Linux kernel for Apalis and Colibri modules srcu: Avoid local_irq_save() before acquiring spinlock_t 2020-06-29T19:01:22+00:00 Sebastian Andrzej Siewior bigeasy@linutronix.de 2020-05-26T13:41:34+00:00 bde50d8ff83e4ce9e576f7c5ba1edb48a3610a5b SRCU disables interrupts to get a stable per-CPU pointer and then acquires the spinlock which is in the per-CPU data structure. The release uses spin_unlock_irqrestore(). While this is correct on a non-RT kernel, this conflicts with the RT semantics because the spinlock is converted to a 'sleeping' spinlock. Sleeping locks can obviously not be acquired with interrupts disabled. Acquire the per-CPU pointer `ssp->sda' without disabling preemption and then acquire the spinlock_t of the per-CPU data structure. The lock will ensure that the data is consistent. The added call to check_init_srcu_struct() is now needed because a statically defined srcu_struct may remain uninitialized until this point and the newly introduced locking operation requires an initialized spinlock_t. This change was tested for four hours with 8*SRCU-N and 8*SRCU-P without causing any warnings. Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: rcu@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
SRCU disables interrupts to get a stable per-CPU pointer and then
acquires the spinlock which is in the per-CPU data structure. The
release uses spin_unlock_irqrestore(). While this is correct on a non-RT
kernel, this conflicts with the RT semantics because the spinlock is
converted to a 'sleeping' spinlock. Sleeping locks can obviously not be
acquired with interrupts disabled.

Acquire the per-CPU pointer `ssp->sda' without disabling preemption and
then acquire the spinlock_t of the per-CPU data structure. The lock will
ensure that the data is consistent.

The added call to check_init_srcu_struct() is now needed because a
statically defined srcu_struct may remain uninitialized until this
point and the newly introduced locking operation requires an initialized
spinlock_t.

This change was tested for four hours with 8*SRCU-N and 8*SRCU-P without
causing any warnings.

Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: rcu@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
srcu: Fix a typo in comment "amoritized"->"amortized" 2020-06-29T19:01:22+00:00 Ethon Paul ethp@qq.com 2020-04-18T11:46:47+00:00 7fef6cff8f2814bf8eb632e2bb8f0a987ffd9ece This commit fixes a typo in a comment. Signed-off-by: Ethon Paul <ethp@qq.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
This commit fixes a typo in a comment.

Signed-off-by: Ethon Paul <ethp@qq.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
srcu: Add data_race() to ->srcu_lock_count and ->srcu_unlock_count arrays 2020-04-27T18:01:16+00:00 Paul E. McKenney paulmck@kernel.org 2020-01-04T00:36:59+00:00 b68c6146512d92f6d570d26e1873497ade2cc4cb The srcu_data structure's ->srcu_lock_count and ->srcu_unlock_count arrays are read and written locklessly, so this commit adds the data_race() to the diagnostic-print loads from these arrays in order mark them as known and approved data-racy accesses. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely and due to this being used only by rcutorture. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The srcu_data structure's ->srcu_lock_count and ->srcu_unlock_count arrays
are read and written locklessly, so this commit adds the data_race()
to the diagnostic-print loads from these arrays in order mark them as
known and approved data-racy accesses.

This data race was reported by KCSAN. Not appropriate for backporting due
to failure being unlikely and due to this being used only by rcutorture.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
srcu: Add KCSAN stubs 2020-04-27T18:01:15+00:00 Paul E. McKenney paulmck@kernel.org 2020-04-13T23:33:01+00:00 4f58820fd710e0563e22420c07c03c5ccec948bf This commit adds stubs for KCSAN's data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS() macros to allow code using these macros to move ahead. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
This commit adds stubs for KCSAN's data_race(), ASSERT_EXCLUSIVE_WRITER(),
and ASSERT_EXCLUSIVE_ACCESS() macros to allow code using these macros to
move ahead.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Merge branches 'doc.2020.02.27a', 'fixes.2020.03.21a', 'kfree_rcu.2020.02.20a', 'locktorture.2020.02.20a', 'ovld.2020.02.20a', 'rcu-tasks.2020.02.20a', 'srcu.2020.02.20a' and 'torture.2020.02.20a' into HEAD 2020-03-22T00:15:11+00:00 Paul E. McKenney paulmck@kernel.org 2020-03-22T00:15:11+00:00 aa93ec620be378cce1454286122915533ff8fa48 doc.2020.02.27a: Documentation updates. fixes.2020.03.21a: Miscellaneous fixes. kfree_rcu.2020.02.20a: Updates to kfree_rcu(). locktorture.2020.02.20a: Lock torture-test updates. ovld.2020.02.20a: Updates to callback-overload handling. rcu-tasks.2020.02.20a: RCU-tasks updates. srcu.2020.02.20a: SRCU updates. torture.2020.02.20a: Torture-test updates. 
doc.2020.02.27a: Documentation updates.
fixes.2020.03.21a: Miscellaneous fixes.
kfree_rcu.2020.02.20a: Updates to kfree_rcu().
locktorture.2020.02.20a: Lock torture-test updates.
ovld.2020.02.20a: Updates to callback-overload handling.
rcu-tasks.2020.02.20a: RCU-tasks updates.
srcu.2020.02.20a: SRCU updates.
torture.2020.02.20a: Torture-test updates.
srcu: Hold srcu_struct ->lock when updating ->srcu_gp_seq 2020-02-21T00:01:11+00:00 Paul E. McKenney paulmck@kernel.org 2020-01-03T19:42:05+00:00 710426068dc60f2d2e139478d6185710802cdc0a A read of the srcu_struct structure's ->srcu_gp_seq field should not need READ_ONCE() when that structure's ->lock is held. Except that this lock is not always held when updating this field. This commit therefore acquires the lock around updates and removes a now-unneeded READ_ONCE(). This data race was reported by KCSAN. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> [ paulmck: Switch from READ_ONCE() to lock per Peter Zilstra question. ] Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> 
A read of the srcu_struct structure's ->srcu_gp_seq field should not
need READ_ONCE() when that structure's ->lock is held.  Except that this
lock is not always held when updating this field.  This commit therefore
acquires the lock around updates and removes a now-unneeded READ_ONCE().

This data race was reported by KCSAN.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ paulmck: Switch from READ_ONCE() to lock per Peter Zilstra question. ]
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
srcu: Fix process_srcu()/srcu_batches_completed() datarace 2020-02-21T00:01:11+00:00 Paul E. McKenney paulmck@kernel.org 2019-12-23T03:39:35+00:00 39f91504a03a7a2abdb52205106942fa4a548d0d The srcu_struct structure's ->srcu_idx field is accessed locklessly, so reads must use READ_ONCE(). This commit therefore adds the needed READ_ONCE() invocation where it was missed. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The srcu_struct structure's ->srcu_idx field is accessed locklessly,
so reads must use READ_ONCE().  This commit therefore adds the needed
READ_ONCE() invocation where it was missed.

This data race was reported by KCSAN.  Not appropriate for backporting
due to failure being unlikely.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
srcu: Fix __call_srcu()/srcu_get_delay() datarace 2020-02-21T00:01:11+00:00 Paul E. McKenney paulmck@kernel.org 2019-12-23T03:36:33+00:00 8c9e0cb32315835825ea1ad725a858a2d2ce4a8e The srcu_struct structure's ->srcu_gp_seq_needed_exp field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_ONCE() invocations. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The srcu_struct structure's ->srcu_gp_seq_needed_exp field is accessed
locklessly, so updates must use WRITE_ONCE().  This commit therefore
adds the needed WRITE_ONCE() invocations.

This data race was reported by KCSAN.  Not appropriate for backporting
due to failure being unlikely.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
srcu: Fix __call_srcu()/process_srcu() datarace 2020-02-21T00:01:11+00:00 Paul E. McKenney paulmck@kernel.org 2019-12-23T03:32:54+00:00 7ff8b4502bc0f576450d4ecbda97fa30e8002ed1 The srcu_node structure's ->srcu_gp_seq_needed_exp field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_ONCE() invocations. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The srcu_node structure's ->srcu_gp_seq_needed_exp field is accessed
locklessly, so updates must use WRITE_ONCE().  This commit therefore
adds the needed WRITE_ONCE() invocations.

This data race was reported by KCSAN.  Not appropriate for backporting
due to failure being unlikely.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
rcu: Fix typos in file-header comments 2020-02-20T23:58:22+00:00 SeongJae Park sjpark@amazon.de 2020-01-06T20:08:02+00:00 65bb0dc437c3e57a6cde2b81170c8af4b9c90735 Convert to plural and add a note that this is for Tree RCU. Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Convert to plural and add a note that this is for Tree RCU.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>