linux/kernel/rcu/srcutree.c, branch v5.11

Merge branches 'cpuinfo.2020.11.06a', 'doc.2020.11.06a', 'fixes.2020.11.19b', 'lockdep.2020.11.02a', 'tasks.2020.11.06a' and 'torture.2020.11.06a' into HEAD

2020-11-20T03:37:47Z

cpuinfo.2020.11.06a: Speedups for /proc/cpuinfo. doc.2020.11.06a: Documentation updates. fixes.2020.11.19b: Miscellaneous fixes. lockdep.2020.11.02a: Lockdep-RCU updates to avoid "unused variable". tasks.2020.11.06a: Tasks-RCU updates. torture.2020.11.06a': Torture-test updates.

srcu: Take early exit on memory-allocation failure

2020-11-20T03:37:17Z

It turns out that init_srcu_struct() can be invoked from usermode tasks, and that fatal signals received by these tasks can cause memory-allocation failures. These failures are not handled well by init_srcu_struct(), so much so that NULL pointer dereferences can result. This commit therefore causes init_srcu_struct() to take an early exit upon detection of memory-allocation failure. Link: https://lore.kernel.org/lkml/20200908144306.33355-1-aik@ozlabs.ru/ Reported-by: Alexey Kardashevskiy Tested-by: Alexey Kardashevskiy Signed-off-by: Paul E. McKenney

srcu: Use a more appropriate lockdep helper

2020-11-03T01:10:00Z

The lockdep_is_held() macro is defined as: #define lockdep_is_held(lock) lock_is_held(&(lock)->dep_map) This hides away the dereference, so that builds with !LOCKDEP don't break. This works in current kernels because the RCU_LOCKDEP_WARN() eliminates its condition at preprocessor time in !LOCKDEP kernels. However, later patches in this series will cause the compiler to see this condition even in !LOCKDEP kernels. This commit prepares for this upcoming change by switching from lock_is_held() to lockdep_is_held(). Signed-off-by: Jakub Kicinski -- CC: jiangshanlai@gmail.com CC: paulmck@kernel.org CC: josh@joshtriplett.org CC: rostedt@goodmis.org CC: mathieu.desnoyers@efficios.com Signed-off-by: Paul E. McKenney

srcu: Remove KCSAN stubs

2020-08-25T01:36:03Z

KCSAN is now in mainline, so this commit removes the stubs for the data_race(), ASSERT_EXCLUSIVE_WRITER(), and ASSERT_EXCLUSIVE_ACCESS() macros. Signed-off-by: Paul E. McKenney

srcu: Avoid local_irq_save() before acquiring spinlock_t

2020-06-29T19:01:22Z

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 Cc: "Paul E. McKenney" Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: rcu@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney

srcu: Fix a typo in comment "amoritized"->"amortized"

2020-06-29T19:01:22Z

This commit fixes a typo in a comment. Signed-off-by: Ethon Paul Signed-off-by: Paul E. McKenney

srcu: Add data_race() to ->srcu_lock_count and ->srcu_unlock_count arrays

2020-04-27T18:01:16Z

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

srcu: Add KCSAN stubs

2020-04-27T18:01:15Z

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

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

2020-03-22T00:15:11Z

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

2020-02-21T00:01:11Z

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: Switch from READ_ONCE() to lock per Peter Zilstra question. ] Acked-by: Peter Zijlstra (Intel)