user/sven/linux.git/include/linux/rcupdate.h, branch v3.18.33

rcu: Move lockless_dereference() out of rcupdate.h

2015-09-27T16:18:53Z

[ Upstream commit 0a04b0166929405cd833c1cc40f99e862b965ddc ] I want to use lockless_dereference() from seqlock.h, which would mean including rcupdate.h from it, however rcupdate.h already includes seqlock.h. Avoid this by moving lockless_dereference() into compiler.h. This is somewhat tricky since it uses smp_read_barrier_depends() which isn't available there, but its a CPP macro so we can get away with it. The alternative would be moving it into asm/barrier.h, but that would be updating each arch (I can do if people feel that is more appropriate). Cc: Paul McKenney Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Rusty Russell Signed-off-by: Sasha Levin

rcu: Provide counterpart to rcu_dereference() for non-RCU situations

2014-10-28T22:25:17Z

Although rcu_dereference() and friends can be used in situations where object lifetimes are being managed by something other than RCU, the resulting sparse and lockdep-RCU noise can be annoying. This commit therefore supplies a lockless_dereference(), which provides the protection for dereferences without the RCU-related debugging noise. Reported-by: Al Viro Signed-off-by: Paul E. McKenney Signed-off-by: Al Viro

rcutorture: Rename rcutorture_runnable parameter

2014-09-16T20:41:44Z

This commit changes rcutorture_runnable to torture_runnable, which is consistent with the names of the other parameters and is a bit shorter as well. Signed-off-by: Paul E. McKenney

Merge branch 'rcu-tasks.2014.09.10a' into HEAD

2014-09-16T17:10:44Z

rcu-tasks.2014.09.10a: Add RCU-tasks flavor of RCU.

Merge branches 'doc.2014.09.07a', 'fixes.2014.09.10a', 'nocb-nohz.2014.09.16b' and 'torture.2014.09.07a' into HEAD

2014-09-16T17:08:34Z

doc.2014.09.07a: Documentation updates. fixes.2014.09.10a: Miscellaneous fixes. nocb-nohz.2014.09.16b: No-CBs CPUs and NO_HZ_FULL updates. torture.2014.09.07a: Torture-test updates.

rcu: Fix attempt to avoid unsolicited offloading of callbacks

2014-09-16T17:07:59Z

Commit b58cc46c5f6b (rcu: Don't offload callbacks unless specifically requested) failed to adjust the callback lists of the CPUs that are known to be no-CBs CPUs only because they are also nohz_full= CPUs. This failure can result in callbacks that are posted during early boot getting stranded on nxtlist for CPUs whose no-CBs property becomes apparent late, and there can also be spurious warnings about offline CPUs posting callbacks. This commit fixes these problems by adding an early-boot rcu_init_nohz() that properly initializes the no-CBs CPUs. Note that kernels built with CONFIG_RCU_NOCB_CPU_ALL=y or with CONFIG_RCU_NOCB_CPU=n do not exhibit this bug. Neither do kernels booted without the nohz_full= boot parameter. Signed-off-by: Paul E. McKenney Reviewed-by: Pranith Kumar Tested-by: Paul Gortmaker

rcu: Per-CPU operation cleanups to rcu_*_qs() functions

2014-09-07T23:27:35Z

The rcu_bh_qs(), rcu_preempt_qs(), and rcu_sched_qs() functions use old-style per-CPU variable access and write to ->passed_quiesce even if it is already set. This commit therefore updates to use the new-style per-CPU variable access functions and avoids the spurious writes. This commit also eliminates the "cpu" argument to these functions because they are always invoked on the indicated CPU. Reported-by: Peter Zijlstra Signed-off-by: Paul E. McKenney

rcu: Remove redundant preempt_disable() from rcu_note_voluntary_context_switch()

2014-09-07T23:27:32Z

In theory, synchronize_sched() requires a read-side critical section to order against. In practice, preemption can be thought of as being disabled across every machine instruction, at least for those machine instructions that are not in the idle loop and not on offline CPUs. So this commit removes the redundant preempt_disable() from rcu_note_voluntary_context_switch(). Please note that the single instruction in question is the store of zero to ->rcu_tasks_holdout. The "if" is simply a performance optimization that avoids unnecessary stores. To see this, keep in mind that both the "if" condition and the store are in a quiescent state. Therefore, even if the task is preempted for a full grace period (presumably due to its having done a context switch beforehand), the store will be recording a legitimate quiescent state. Reported-by: Lai Jiangshan Signed-off-by: Paul E. McKenney Conflicts: include/linux/rcupdate.h

rcutorture: Add torture tests for RCU-tasks

2014-09-07T23:27:24Z

This commit adds torture tests for RCU-tasks. It also fixes a bug that would segfault for an RCU flavor lacking a callback-barrier function. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Make TASKS_RCU handle tasks that are almost done exiting

2014-09-07T23:27:22Z

Once a task has passed exit_notify() in the do_exit() code path, it is no longer on the task lists, and is therefore no longer visible to rcu_tasks_kthread(). This means that an almost-exited task might be preempted while within a trampoline, and this task won't be waited on by rcu_tasks_kthread(). This commit fixes this bug by adding an srcu_struct. An exiting task does srcu_read_lock() just before calling exit_notify(), and does the corresponding srcu_read_unlock() after doing the final preempt_disable(). This means that rcu_tasks_kthread() can do synchronize_srcu() to wait for all mostly-exited tasks to reach their final preempt_disable() region, and then use synchronize_sched() to wait for those tasks to finish exiting. Reported-by: Oleg Nesterov Suggested-by: Lai Jiangshan Signed-off-by: Paul E. McKenney