- 12 2月, 2015 1 次提交
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由 Paul E. McKenney 提交于
If the scheduling-clock interrupt sets the current tasks need_qs flag, but if the current CPU passes through a quiescent state in the meantime, then rcu_preempt_qs() will fail to clear the need_qs flag, which can fool RCU into thinking that additional rcu_read_unlock_special() processing is needed. This commit therefore clears the need_qs flag before checking for additional processing. For this problem to occur, we need rcu_preempt_data.passed_quiesce equal to true and current->rcu_read_unlock_special.b.need_qs also equal to true. This condition can occur as follows: 1. CPU 0 is aware of the current preemptible RCU grace period, but has not yet passed through a quiescent state. Among other things, this means that rcu_preempt_data.passed_quiesce is false. 2. Task A running on CPU 0 enters a preemptible RCU read-side critical section. 3. CPU 0 takes a scheduling-clock interrupt, which notices the RCU read-side critical section and the need for a quiescent state, and thus sets current->rcu_read_unlock_special.b.need_qs to true. 4. Task A is preempted, enters the scheduler, eventually invoking rcu_preempt_note_context_switch() which in turn invokes rcu_preempt_qs(). Because rcu_preempt_data.passed_quiesce is false, control enters the body of the "if" statement, which sets rcu_preempt_data.passed_quiesce to true. 5. At this point, CPU 0 takes an interrupt. The interrupt handler contains an RCU read-side critical section, and the rcu_read_unlock() notes that current->rcu_read_unlock_special is nonzero, and thus invokes rcu_read_unlock_special(). 6. Once in rcu_read_unlock_special(), the fact that current->rcu_read_unlock_special.b.need_qs is true becomes apparent, so rcu_read_unlock_special() invokes rcu_preempt_qs(). Recursively, given that we interrupted out of that same function in the preceding step. 7. Because rcu_preempt_data.passed_quiesce is now true, rcu_preempt_qs() does nothing, and simply returns. 8. Upon return to rcu_read_unlock_special(), it is noted that current->rcu_read_unlock_special is still nonzero (because the interrupted rcu_preempt_qs() had not yet gotten around to clearing current->rcu_read_unlock_special.b.need_qs). 9. Execution proceeds to the WARN_ON_ONCE(), which notes that we are in an interrupt handler and thus duly splats. The solution, as noted above, is to make rcu_read_unlock_special() clear out current->rcu_read_unlock_special.b.need_qs after calling rcu_preempt_qs(). The interrupted rcu_preempt_qs() will clear it again, but this is harmless. The worst that happens is that we clobber another attempt to set this field, but this is not a problem because we just got done reporting a quiescent state. Reported-by: NSasha Levin <sasha.levin@oracle.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Fix embarrassing build bug noted by Sasha Levin. ] Tested-by: NSasha Levin <sasha.levin@oracle.com>
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- 16 1月, 2015 1 次提交
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由 Paul E. McKenney 提交于
Recent testing has shown that under heavy load, running RCU's grace-period kthreads at real-time priority can improve performance (according to 0day test robot) and reduce the incidence of RCU CPU stall warnings. However, most systems do just fine with the default non-realtime priorities for these kthreads, and it does not make sense to expose the entire user base to any risk stemming from this change, given that this change is of use only to a few users running extremely heavy workloads. Therefore, this commit allows users to specify realtime priorities for the grace-period kthreads, but leaves them running SCHED_OTHER by default. The realtime priority may be specified at build time via the RCU_KTHREAD_PRIO Kconfig parameter, or at boot time via the rcutree.kthread_prio parameter. Either way, 0 says to continue the default SCHED_OTHER behavior and values from 1-99 specify that priority of SCHED_FIFO behavior. Note that a value of 0 is not permitted when the RCU_BOOST Kconfig parameter is specified. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 11 1月, 2015 2 次提交
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由 Paul E. McKenney 提交于
Currently, rcutorture's Reader Batch checks measure from the end of the previous grace period to the end of the current one. This commit tightens up these checks by measuring from the start and end of the same grace period. This involves adding rcu_batches_started() and friends corresponding to the existing rcu_batches_completed() and friends. We leave SRCU alone for the moment, as it does not yet have a way of tracking both ends of its grace periods. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Long ago, the various ->completed fields were of type long, but now are unsigned long due to signed-integer-overflow concerns. However, the various _batches_completed() functions remained of type long, even though their only purpose in life is to return the corresponding ->completed field. This patch cleans this up by changing these functions' return types to unsigned long. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 07 1月, 2015 12 次提交
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由 Paul E. McKenney 提交于
Subtle race conditions can result if a CPU stays in dyntick-idle mode long enough for the ->gpnum and ->completed fields to wrap. For example, consider the following sequence of events: o CPU 1 encounters a quiescent state while waiting for grace period 5 to complete, but then enters dyntick-idle mode. o While CPU 1 is in dyntick-idle mode, the grace-period counters wrap around so that the grace period number is now 4. o Just as CPU 1 exits dyntick-idle mode, grace period 4 completes and grace period 5 begins. o The quiescent state that CPU 1 passed through during the old grace period 5 looks like it applies to the new grace period 5. Therefore, the new grace period 5 completes without CPU 1 having passed through a quiescent state. This could clearly be a fatal surprise to any long-running RCU read-side critical section that happened to be running on CPU 1 at the time. At one time, this was not a problem, given that it takes significant time for the grace-period counters to overflow even on 32-bit systems. However, with the advent of NO_HZ_FULL and SMP embedded systems, arbitrarily long idle periods are now becoming quite feasible. It is therefore time to close this race. This commit therefore avoids this race condition by having the quiescent-state forcing code detect when a CPU is falling too far behind, and setting a new rcu_data field ->gpwrap when this happens. Whenever this new ->gpwrap field is set, the CPU's ->gpnum and ->completed fields are known to be untrustworthy, and can be ignored, along with any associated quiescent states. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
One way that an RCU CPU stall warning can happen is if the grace-period kthread is not allowed to execute. One proxy for this kthread's forward progress is the number of force-quiescent-state (fqs) scans. This commit therefore adds the number of fqs scans to the RCU CPU stall warning printouts when CONFIG_RCU_CPU_STALL_INFO=y. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Lai Jiangshan 提交于
The patch dfeb9765 ("Allow post-unlock reference for rt_mutex") ensured rcu-boost safe even the rt_mutex has post-unlock reference. But rt_mutex allowing post-unlock reference is definitely a bug and it was fixed by the commit 27e35715 ("rtmutex: Plug slow unlock race"). This fix made the previous patch (dfeb9765) useless. And even worse, the priority-inversion introduced by the the previous patch still exists. rcu_read_unlock_special() { rt_mutex_unlock(&rnp->boost_mtx); /* Priority-Inversion: * the current task had been deboosted and preempted as a low * priority task immediately, it could wait long before reschedule in, * and the rcu-booster also waits on this low priority task and sleeps. * This priority-inversion makes rcu-booster can't work * as expected. */ complete(&rnp->boost_completion); } Just revert the patch to avoid it. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
When rcu_boost_kthread_setaffinity() sees that all CPUs for a given rcu_node structure are now offline, it affinities the corresponding RCU-boost ("rcub") kthread away from those CPUs. This is pointless because the kthread cannot run on those offline CPUs in any case. This commit therefore removes this unneeded code. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Now that offlining CPUs no longer moves leaf rcu_node structures' ->blkd_tasks lists to the root, there is no way for the root rcu_node structure's ->blkd_task list to be nonempty, unless the root node is also the sole leaf node. This commit therefore refrains from creating an rcub kthread for the root rcu_node structure unless it is also the sole leaf. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Given that there is now arcu_preempt_has_tasks() function that checks to see if the ->blkd_tasks list is non-empty, this commit makes use of it. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
When the last CPU associated with a given leaf rcu_node structure goes offline, something must be done about the tasks queued on that rcu_node structure. Each of these tasks has been preempted on one of the leaf rcu_node structure's CPUs while in an RCU read-side critical section that it have not yet exited. Handling these tasks is the job of rcu_preempt_offline_tasks(), which migrates them from the leaf rcu_node structure to the root rcu_node structure. Unfortunately, this migration has to be done one task at a time because each tasks allegiance must be shifted from the original leaf rcu_node to the root, so that future attempts to deal with these tasks will acquire the root rcu_node structure's ->lock rather than that of the leaf. Worse yet, this migration must be done with interrupts disabled, which is not so good for realtime response, especially given that there is no bound on the number of tasks on a given rcu_node structure's list. (OK, OK, there is a bound, it is just that it is unreasonably large, especially on 64-bit systems.) This was not considered a problem back when rcu_preempt_offline_tasks() was first written because realtime systems were assumed not to do CPU-hotplug operations while real-time applications were running. This assumption has proved of dubious validity given that people are starting to run multiple realtime applications on a single SMP system and that it is common practice to offline then online a CPU before starting its real-time application in order to clear extraneous processing off of that CPU. So we now need CPU hotplug operations to avoid undue latencies. This commit therefore avoids migrating these tasks, instead letting them be dequeued one by one from the original leaf rcu_node structure by rcu_read_unlock_special(). This means that the clearing of bits from the upper-level rcu_node structures must be deferred until the last such task has been dequeued, because otherwise subsequent grace periods won't wait on them. This commit has the beneficial side effect of simplifying the CPU-hotplug code for TREE_PREEMPT_RCU, especially in CONFIG_RCU_BOOST builds. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit causes rcu_read_unlock_special() to propagate ->qsmaskinit bit clearing up the rcu_node tree once a given rcu_node structure's blkd_tasks list becomes empty. This is the final commit in preparation for the rework of RCU priority boosting: It enables preempted tasks to remain queued on their rcu_node structure even after all of that rcu_node structure's CPUs have gone offline. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit abstracts rcu_cleanup_dead_rnp() from rcu_cleanup_dead_cpu() in preparation for the rework of RCU priority boosting. This new function will be invoked from rcu_read_unlock_special() in the reworked scheme, which is why rcu_cleanup_dead_rnp() assumes that the leaf rcu_node structure's ->qsmaskinit field has already been updated. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit undertakes a simple variable renaming to make way for some rework of RCU priority boosting. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
This commit prevents random compiler optimizations by applying ACCESS_ONCE() to lockless accesses. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The rcu_barrier() no-callbacks check for no-CBs CPUs has race conditions. It checks a given CPU's lists of callbacks, and if all three no-CBs lists are empty, ignores that CPU. However, these three lists could potentially be empty even when callbacks are present if the check executed just as the callbacks were being moved from one list to another. It turns out that recent versions of rcutorture can spot this race. This commit plugs this hole by consolidating the per-list counts of no-CBs callbacks into a single count, which is incremented before the corresponding callback is posted and after it is invoked. Then rcu_barrier() checks this single count to reliably determine whether the corresponding CPU has no-CBs callbacks. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 04 11月, 2014 6 次提交
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由 Paul E. McKenney 提交于
The "cpu" argument to rcu_cleanup_after_idle() is always the current CPU, so drop it. This moves the smp_processor_id() from the caller to rcu_cleanup_after_idle(), saving argument-passing overhead. Again, the anticipated cross-CPU uses of these functions has been replaced by NO_HZ_FULL. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
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由 Paul E. McKenney 提交于
The "cpu" argument to rcu_prepare_for_idle() is always the current CPU, so drop it. This in turn allows two of the uses of "cpu" in this function to be replaced with a this_cpu_ptr() and the third by smp_processor_id(), replacing that of the call to rcu_prepare_for_idle(). Again, the anticipated cross-CPU uses of these functions has been replaced by NO_HZ_FULL. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
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由 Paul E. McKenney 提交于
The "cpu" argument to rcu_needs_cpu() is always the current CPU, so drop it. This in turn allows the "cpu" argument to rcu_cpu_has_callbacks() to be removed, which allows the uses of "cpu" in both functions to be replaced with a this_cpu_ptr(). Again, the anticipated cross-CPU uses of these functions has been replaced by NO_HZ_FULL. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
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由 Paul E. McKenney 提交于
The "cpu" argument to rcu_note_context_switch() is always the current CPU, so drop it. This in turn allows the "cpu" argument to rcu_preempt_note_context_switch() to be removed, which allows the sole use of "cpu" in both functions to be replaced with a this_cpu_ptr(). Again, the anticipated cross-CPU uses of these functions has been replaced by NO_HZ_FULL. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
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由 Paul E. McKenney 提交于
Because rcu_preempt_check_callbacks()'s argument is guaranteed to always be the current CPU, drop the argument and replace per_cpu() with __this_cpu_read(). Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
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由 Christoph Lameter 提交于
For some functions in kernel/rcu/tree* the rdtp parameter is always this_cpu_ptr(rdtp). Remove the parameter if constant and calculate the pointer in function. This will have the advantage that it is obvious that the address are all per cpu offsets and thus it will enable the use of this_cpu_ops in the future. Signed-off-by: NChristoph Lameter <cl@linux.com> [ paulmck: Forward-ported to rcu/dev, whitespace adjustment. ] Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com>
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- 30 10月, 2014 3 次提交
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由 Paul E. McKenney 提交于
Commit 35ce7f29 (rcu: Create rcuo kthreads only for onlined CPUs) contains checks for the case where CPUs are brought online out of order, re-wiring the rcuo leader-follower relationships as needed. Unfortunately, this rewiring was broken. This apparently went undetected due to the tendency of systems to bring CPUs online in order. This commit nevertheless fixes the rewiring. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Pranith Kumar 提交于
PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU and uses PREEMPT_RCU config option in its place. Signed-off-by: NPranith Kumar <bobby.prani@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Clark Williams 提交于
Rename CONFIG_RCU_BOOST_PRIO to CONFIG_RCU_KTHREAD_PRIO and use this value for both the per-CPU kthreads (rcuc/N) and the rcu boosting threads (rcub/n). Also, create the module_parameter rcutree.kthread_prio to be used on the kernel command line at boot to set a new value (rcutree.kthread_prio=N). Signed-off-by: NClark Williams <clark.williams@gmail.com> [ paulmck: Ported to rcu/dev, applied Paul Bolle and Peter Zijlstra feedback. ] Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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- 29 10月, 2014 3 次提交
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由 Paul E. McKenney 提交于
There are some RCU_BOOST-specific per-CPU variable declarations that are needlessly defined under #ifdef in kernel/rcu/tree.c. This commit therefore moves these declarations into a pre-existing #ifdef in kernel/rcu/tree_plugin.h. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
The CONFIG_RCU_CPU_STALL_VERBOSE Kconfig parameter causes preemptible RCU's CPU stall warnings to dump out any preempted tasks that are blocking the current RCU grace period. This information is useful, and the default has been CONFIG_RCU_CPU_STALL_VERBOSE=y for some years. It is therefore time for this commit to remove this Kconfig parameter, so that future kernel builds will always act as if CONFIG_RCU_CPU_STALL_VERBOSE=y. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
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由 Paul E. McKenney 提交于
Commit 35ce7f29 (rcu: Create rcuo kthreads only for onlined CPUs) avoids creating rcuo kthreads for CPUs that never come online. This fixes a bug in many instances of firmware: Instead of lying about their age, these systems instead lie about the number of CPUs that they have. Before commit 35ce7f29, this could result in huge numbers of useless rcuo kthreads being created. It appears that experience indicates that I should have told the people suffering from this problem to fix their broken firmware, but I instead produced what turned out to be a partial fix. The missing piece supplied by this commit makes sure that rcu_barrier() knows not to post callbacks for no-CBs CPUs that have not yet come online, because otherwise rcu_barrier() will hang on systems having firmware that lies about the number of CPUs. It is tempting to simply have rcu_barrier() refuse to post a callback on any no-CBs CPU that does not have an rcuo kthread. This unfortunately does not work because rcu_barrier() is required to wait for all pending callbacks. It is therefore required to wait even for those callbacks that cannot possibly be invoked. Even if doing so hangs the system. Given that posting a callback to a no-CBs CPU that does not yet have an rcuo kthread can hang rcu_barrier(), It is tempting to report an error in this case. Unfortunately, this will result in false positives at boot time, when it is perfectly legal to post callbacks to the boot CPU before the scheduler has started, in other words, before it is legal to invoke rcu_barrier(). So this commit instead has rcu_barrier() avoid posting callbacks to CPUs having neither rcuo kthread nor pending callbacks, and has it complain bitterly if it finds CPUs having no rcuo kthread but some pending callbacks. And when rcu_barrier() does find CPUs having no rcuo kthread but pending callbacks, as noted earlier, it has no choice but to hang indefinitely. Reported-by: NYanko Kaneti <yaneti@declera.com> Reported-by: NJay Vosburgh <jay.vosburgh@canonical.com> Reported-by: NMeelis Roos <mroos@linux.ee> Reported-by: NEric B Munson <emunson@akamai.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NEric B Munson <emunson@akamai.com> Tested-by: NJay Vosburgh <jay.vosburgh@canonical.com> Tested-by: NYanko Kaneti <yaneti@declera.com> Tested-by: NKevin Fenzi <kevin@scrye.com> Tested-by: NMeelis Roos <mroos@linux.ee>
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- 19 9月, 2014 1 次提交
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由 Paul E. McKenney 提交于
Currently, the expedited grace-period primitives do get_online_cpus(). This greatly simplifies their implementation, but means that calls to them holding locks that are acquired by CPU-hotplug notifiers (to say nothing of calls to these primitives from CPU-hotplug notifiers) can deadlock. But this is starting to become inconvenient, as can be seen here: https://lkml.org/lkml/2014/8/5/754. The problem in this case is that some developers need to acquire a mutex from a CPU-hotplug notifier, but also need to hold it across a synchronize_rcu_expedited(). As noted above, this currently results in deadlock. This commit avoids the deadlock and retains the simplicity by creating a try_get_online_cpus(), which returns false if the get_online_cpus() reference count could not immediately be incremented. If a call to try_get_online_cpus() returns true, the expedited primitives operate as before. If a call returns false, the expedited primitives fall back to normal grace-period operations. This falling back of course results in increased grace-period latency, but only during times when CPU hotplug operations are actually in flight. The effect should therefore be negligible during normal operation. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Tested-by: NLan Tianyu <tianyu.lan@intel.com>
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- 17 9月, 2014 11 次提交
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由 Paul E. McKenney 提交于
The NOCB follower wakeup ordering depends on the store to the tail pointer happening before the wakeup. However, because atomic_long_add() does not return a value, it does not provide ordering guarantees, and the locking in wake_up() only guarantees that the store will happen before the unlock, which might be too late. Even though this is only a theoretical issue, this commit adds a smp_mb__after_atomic() after the final atomic_long_add() to provide the needed ordering guarantee. Reported-by: NAmit Shah <amit.shah@redhat.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Paul E. McKenney 提交于
If an RCU callback is queued on a no-CBs CPU from idle code with irqs disabled, and if that CPU stays idle forever after, the callback will never be invoked. This commit therefore adds a check for this situation in ____call_rcu_nocb(), invoking the RCU core solely for the purpose of the ensuing return-to-idle transition. (If the CPU doesn't return to idle, the next scheduling-clock interrupt will fix things up.) Reported-by: NAmit Shah <amit.shah@redhat.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Paul E. McKenney 提交于
The NOCB leader wakeup ordering depends on the store to the header happening before the check for the leader already being awake. However, because atomic_long_add() does not return a value, it does not provide ordering guarantees, the incorrect comment in wake_nocb_leader() notwithstanding. This commit therefore adds a smp_mb__after_atomic() after the final atomic_long_add() to provide the needed ordering guarantee. Reported-by: NAmit Shah <amit.shah@redhat.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Paul E. McKenney 提交于
If there are no nohz_full= CPUs, then there is currently no reason to track sysidle state. This commit therefore short-circuits this state tracking if !tick_nohz_full_enabled(). Note that these checks will need to be revisited if nohz_full= state can ever be changed at runtime. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: NFrederic Weisbecker <fweisbec@gmail.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Paul E. McKenney 提交于
Now that we have rcu_state_p, which references rcu_preempt_state for TREE_PREEMPT_RCU and rcu_sched_state for TREE_RCU, we don't need a separate rcu_sysidle_state variable. This commit therefore eliminates rcu_preempt_state in favor of rcu_state_p. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NPranith Kumar <bobby.prani@gmail.com> Acked-by: NFrederic Weisbecker <fweisbec@gmail.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Pranith Kumar 提交于
If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the cpumask rcu_nocb_mask can be garbage instead of NULL. Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for have_rcu_nocb_mask. Signed-off-by: NPranith Kumar <bobby.prani@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Paul E. McKenney 提交于
RCU currently uses for_each_possible_cpu() to spawn rcuo kthreads, which can result in more rcuo kthreads than one would expect, for example, derRichard reported 64 CPUs worth of rcuo kthreads on an 8-CPU image. This commit therefore creates rcuo kthreads only for those CPUs that actually come online. This was reported by derRichard on the OFTC IRC network. Reported-by: NRichard Weinberger <richard@nod.at> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Paul E. McKenney 提交于
Currently, RCU spawns kthreads from several different early_initcall() functions. Although this has served RCU well for quite some time, as more kthreads are added a more deterministic approach is required. This commit therefore causes all of RCU's early-boot kthreads to be spawned from a single early_initcall() function. Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: NJosh Triplett <josh@joshtriplett.org> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Pranith Kumar 提交于
Return false instead of 0 in rcu_nocb_adopt_orphan_cbs() as this has bool as return type. Signed-off-by: NPranith Kumar <bobby.prani@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Pranith Kumar 提交于
Return false instead of 0 in __call_rcu_nocb() as this has bool as return type. Signed-off-by: NPranith Kumar <bobby.prani@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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由 Pranith Kumar 提交于
Return true/false in rcu_nocb_adopt_orphan_cbs() instead of 0/1 as this function has return type of bool. Signed-off-by: NPranith Kumar <bobby.prani@gmail.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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