summaryrefslogtreecommitdiffstats
path: root/kernel/rcu
Commit message (Collapse)AuthorAgeFilesLines
*-----. Merge branches 'consolidate.2019.04.09a', 'doc.2019.03.26b', ↵Paul E. McKenney2019-04-0912-826/+827
|\ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'fixes.2019.03.26b', 'srcu.2019.03.26b', 'stall.2019.03.26b' and 'torture.2019.03.26b' into HEAD consolidate.2019.04.09a: Lingering RCU flavor consolidation cleanups. doc.2019.03.26b: Documentation updates. fixes.2019.03.26b: Miscellaneous fixes. srcu.2019.03.26b: SRCU updates. stall.2019.03.26b: RCU CPU stall warning updates. torture.2019.03.26b: Torture-test updates.
| | | | * rcuperf: Fix cleanup path for invalid perf_type stringsPaul E. McKenney2019-03-261-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If the specified rcuperf.perf_type is not in the rcu_perf_init() function's perf_ops[] array, rcuperf prints some console messages and then invokes rcu_perf_cleanup() to set state so that a future torture test can run. However, rcu_perf_cleanup() also attempts to end the test that didn't actually start, and in doing so relies on the value of cur_ops, a value that is not particularly relevant in this case. This can result in confusing output or even follow-on failures due to attempts to use facilities that have not been properly initialized. This commit therefore sets the value of cur_ops to NULL in this case and inserts a check near the beginning of rcu_perf_cleanup(), thus avoiding relying on an irrelevant cur_ops value. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | | * rcutorture: Fix cleanup path for invalid torture_type stringsPaul E. McKenney2019-03-261-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If the specified rcutorture.torture_type is not in the rcu_torture_init() function's torture_ops[] array, rcutorture prints some console messages and then invokes rcu_torture_cleanup() to set state so that a future torture test can run. However, rcu_torture_cleanup() also attempts to end the test that didn't actually start, and in doing so relies on the value of cur_ops, a value that is not particularly relevant in this case. This can result in confusing output or even follow-on failures due to attempts to use facilities that have not been properly initialized. This commit therefore sets the value of cur_ops to NULL in this case and inserts a check near the beginning of rcu_torture_cleanup(), thus avoiding relying on an irrelevant cur_ops value. Reported-by: kernel test robot <rong.a.chen@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | | * rcutorture: Fix expected forward progress duration in OOM notifierNeeraj Upadhyay2019-03-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rcutorture_oom_notify() function has a misplaced close parenthesis that results in increasingly long delays in rcu_fwd_progress_check()'s checking for various RCU forward-progress problems. This commit therefore puts the parenthesis in the right place. Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | | * rcutorture: Remove ->ext_irq_conflict fieldPaul E. McKenney2019-03-261-5/+0Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Back when there was a separate RCU-bh flavor, the ->ext_irq_conflict field was used to prevent executing local_bh_enable() while interrupts were disabled. However, there is no longer an RCU-bh flavor, so this commit removes the no-longer-needed ->ext_irq_conflict field. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | | * rcutorture: Make rcutorture_extend_mask() comment match the codePaul E. McKenney2019-03-261-1/+1
| |_|_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The code actually rarely uses more than one type of RCU read-side protection, as is actually desired given that we need some reasonable probability of preempting RCU read-side critical sections, which cannot happen with multiple types of protection. This comment therefore adjusts the comment. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Fix nohz status in stall warningNeeraj Upadhyay2019-03-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The Documentation/RCU/stallwarn.txt file says that stall warnings print "D" if dyntick-idle processing is enabled, but the code in print_cpu_stall_fast_no_hz() prints "." instead. This commit therefore reverses the sense of the test to make the code match the documentation. Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move forward-progress checkers into tree_stall.hPaul E. McKenney2019-03-263-166/+173
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit further consolidates stall-warning functionality by moving forward-progress checkers into kernel/rcu/tree_stall.h, updating a comment or two while in the area. More specifically, this commit moves show_rcu_gp_kthreads(), rcu_check_gp_start_stall(), rcu_fwd_progress_check(), sysrq_rcu, sysrq_show_rcu(), sysrq_rcudump_op, and rcu_sysrq_init() from kernel/rcu/tree.c to kernel/rcu/tree_stall.h. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move irq-disabled stall-warning checking to tree_stall.hPaul E. McKenney2019-03-263-21/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rcu_iw_handler() function's sole purpose in life is to indicate whether a stalled CPU had interrupts disabled, so it belongs in kernel/rcu/tree_stall.h. This commit therefore makes that move, clarifying its header comment while in the area. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Organize functions in tree_stall.hPaul E. McKenney2019-03-262-84/+97
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit does only code movement, removal of now-unneeded forward declarations, and addition of comments. It organizes the functions that implement RCU CPU stall warnings for normal grace periods into three categories: 1. Control of RCU CPU stall warnings, including computing timeouts. 2. Interaction of stall warnings with grace periods. 3. Actual printing of the RCU CPU stall-warning messages. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move FAST_NO_HZ stall-warning code to tree_stall.hPaul E. McKenney2019-03-263-81/+80Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit further consolidates the stall-warning code by moving print_cpu_stall_info() and its helper functions along with zero_cpu_stall_ticks() to kernel/rcu/tree_stall.h. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Inline RCU stall-warning info helper functionsPaul E. McKenney2019-03-263-22/+4Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The print_cpu_stall_info_begin() and print_cpu_stall_info_end() print a single character each onto the console, and are a holdover from a time when RCU CPU stall warning messages could be abbreviated using a long-gone Kconfig option. This commit therefore adds these single characters to already-printed strings in the calling functions, and then eliminates both print_cpu_stall_info_begin() and print_cpu_stall_info_end(). Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move rcu_print_task_exp_stall() to tree_exp.hPaul E. McKenney2019-03-262-31/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Because expedited CPU stall warnings are contained within the kernel/rcu/tree_exp.h file, rcu_print_task_exp_stall() should live there too. This commit carries out the required code motion. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Inline RCU task stall-warning helper functionsPaul E. McKenney2019-03-262-30/+7Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rcu_print_detail_task_stall(), rcu_print_task_stall_begin(), and rcu_print_task_stall_end() functions were defined to allow long-gone Kconfig options to provide an abbreviated RCU CPU stall warning printout. This commit saves a few lines of code by inlining them into their sole callers. While in the area, a useless call of rcu_print_detail_task_stall_rnp() on the root rcu_node structure was eliminated. If there is only one rcu_node structure, its tasks get printed twice, but if there are more, the root rcu_node structure is guaranteed to have an empty list of blocked tasks, hence the uselessness. (Long ago, root rcu_node structures with non-empty ->blkd_tasks lists could happen, but no longer.) Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move RCU CPU stall-warning code out of tree.cPaul E. McKenney2019-03-263-294/+299
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit completes the process of consolidating the code for RCU CPU stall warnings for normal grace periods by moving the remaining such code from kernel/rcu/tree.c to kernel/rcu/tree_stall.h. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move RCU CPU stall-warning code out of tree_plugin.hPaul E. McKenney2019-03-262-90/+95
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The RCU CPU stall-warning code for normal grace periods is currently scattered across two files, due to earlier Tiny RCU support for RCU CPU stall warnings and for old Kconfig options that have long since been retired. Given that it is hard for the lead RCU maintainer to find relevant stall-warning code, it would be good to consolidate it. This commit continues this process by moving stall-warning code from kernel/rcu/tree_plugin.c to a new kernel/rcu/tree_stall.h file. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * rcu: Move RCU CPU stall-warning code out of update.cPaul E. McKenney2019-03-264-58/+66
| |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The RCU CPU stall-warning code for normal grace periods is currently scattered across three files, due to earlier Tiny RCU support for RCU CPU stall warnings and for old Kconfig options that have long since been retired. Given that it is hard for the lead RCU maintainer to find relevant stall-warning code, it would be good to consolidate it. This commit starts this process by moving stall-warning code from kernel/rcu/update.c to a new kernel/rcu/tree_stall.h file. Note that the definitions of rcu_cpu_stall_suppress and rcu_cpu_stall_timeout must remain in kernel/rcu/update.h to provide compatibility for kernel boot parameter lists. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | * srcu: Remove cleanup_srcu_struct_quiesced()Paul E. McKenney2019-03-263-30/+16Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cleanup_srcu_struct_quiesced() function was added because NVME used WQ_MEM_RECLAIM workqueues and SRCU did not, which meant that NVME workqueues waiting on SRCU workqueues could result in deadlocks during low-memory conditions. However, SRCU now also has WQ_MEM_RECLAIM workqueues, so there is no longer a potential for deadlock. Furthermore, it turns out to be extremely hard to use cleanup_srcu_struct_quiesced() correctly due to the fact that SRCU callback invocation accesses the srcu_struct structure's per-CPU data area just after callbacks are invoked. Therefore, the usual practice of using srcu_barrier() to wait for callbacks to be invoked before invoking cleanup_srcu_struct_quiesced() fails because SRCU's callback-invocation workqueue handler might be delayed, which can result in cleanup_srcu_struct_quiesced() being invoked (and thus freeing the per-CPU data) before the SRCU's callback-invocation workqueue handler is finished using that per-CPU data. Nor is this a theoretical problem: KASAN emitted use-after-free warnings because of this problem on actual runs. In short, NVME can now safely invoke cleanup_srcu_struct(), which avoids the use-after-free scenario. And cleanup_srcu_struct_quiesced() is quite difficult to use safely. This commit therefore removes cleanup_srcu_struct_quiesced(), switching its sole user back to cleanup_srcu_struct(). This effectively reverts the following pair of commits: f7194ac32ca2 ("srcu: Add cleanup_srcu_struct_quiesced()") 4317228ad9b8 ("nvme: Avoid flush dependency in delete controller flow") Reported-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Bart Van Assche <bvanassche@acm.org>
| | * srcu: Check for in-flight callbacks in _cleanup_srcu_struct()Paul E. McKenney2019-03-261-0/+2
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If someone fails to drain the corresponding SRCU callbacks (for example, by failing to invoke srcu_barrier()) before invoking either cleanup_srcu_struct() or cleanup_srcu_struct_quiesced(), the resulting diagnostic is an ambiguous use-after-free diagnostic, and even then only if you are running something like KASAN. This commit therefore improves SRCU diagnostics by adding checks for in-flight callbacks at _cleanup_srcu_struct() time. Note that these diagnostics can still be defeated, for example, by invoking call_srcu() concurrently with cleanup_srcu_struct(). Which is a really bad idea, but sometimes all too easy to do. But even then, these diagnostics have at least some probability of catching the problem. Reported-by: Sagi Grimberg <sagi@grimberg.me> Reported-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Bart Van Assche <bvanassche@acm.org>
| * rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_specialPaul E. McKenney2019-03-262-3/+3
| | | | | | | | | | | | | | | | | | | | | | The task_struct structure's ->rcu_read_unlock_special field is only ever read or written by the owning task, but it is accessed both at process and interrupt levels. It may therefore be accessed using plain reads and writes while interrupts are disabled, but must be accessed using READ_ONCE() and WRITE_ONCE() or better otherwise. This commit makes a few adjustments to align with this discipline. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Fix typo in tree_exp.h commentPaul E. McKenney2019-03-261-1/+1
| | | | | | | | | | | | | | This commit changes a rcu_exp_handler() comment from rcu_preempt_defer_qs() to rcu_preempt_deferred_qs() in order to better match reality. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Eliminate redundant NULL-pointer checkPaul E. McKenney2019-03-261-5/+2Star
| | | | | | | | | | | | | | | | Because rcu_wake_cond() checks for a null task_struct pointer, there is no need for its callers to do so. This commit eliminates the redundant check. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Fix force_qs_rnp() header commentZhouyi Zhou2019-03-261-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Previously, threads blocked on offlining CPUS were migrated to the root rcu_node structure, thus requiring RCU priority boosting on this structure. However, since commit d19fb8d1f3f6 ("rcu: Don't migrate blocked tasks even if all corresponding CPUs offline"), RCU does not migrate blocked tasks. Consequently, RCU no longer does RCU priority boosting on the root rcu_node structure as of commit 1be0085b515e ("rcu: Don't initiate RCU priority boosting on root rcu_node"). This commit therefore brings comments for the force_qs_rnp() function's header comment in line with this new no-root-boosting reality. Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com> [ paulmck: Also remove obsolete comment on suppressing new grace periods. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Update jiffies_to_sched_qs and adjust_jiffies_till_sched_qs() commentsPaul E. McKenney2019-03-261-1/+2
| | | | | | | | | | | | | | | | This commit better documents the jiffies_to_sched_qs default-value strategy used by adjust_jiffies_till_sched_qs() Reported-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Default jiffies_to_sched_qs to jiffies_till_sched_qsNeeraj Upadhyay2019-03-261-2/+1Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current code only calls adjust_jiffies_till_sched_qs() if jiffies_till_sched_qs is left at its default value, so when the jiffies_till_sched_qs kernel-boot parameter actually is specified, jiffies_to_sched_qs will be left with the value zero, which will result in useless slowdowns of cond_resched(). This commit therefore changes rcu_init_geometry() to unconditionally invoke adjust_jiffies_till_sched_qs(), which ensures that jiffies_to_sched_qs will be initialized in all cases, thus maintaining good cond_resched() performance. Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Fix self-wakeups for grace-period kthreadNeeraj Upadhyay2019-03-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current rcu_gp_kthread_wake() function uses in_interrupt() and thus does a self-wakeup from all interrupt contexts, including the pointless case where the GP kthread happens to be running with bottom halves disabled, along with the impossible case where the GP kthread is running within an NMI handler (you are not supposed to invoke rcu_gp_kthread_wake() from within an NMI handler. This commit therefore replaces the in_interrupt() with in_irq(), so that the self-wakeups happen only from handlers for hardware interrupts and softirqs. This also makes the code match the comment. Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| * rcu: Report error for bad rcu_nocbs= parameter valuesPaul E. McKenney2019-03-261-2/+10
| | | | | | | | | | | | | | | | | | | | | | This commit prints a console message when cpulist_parse() reports a bad list of CPUs, and sets all CPUs' bits in that case. The reason for setting all CPUs' bits is that this is the safe(r) choice for real-time workloads, which would normally be the ones using the rcu_nocbs= kernel boot parameter. Either way, later RCU console log messages list the actual set of CPUs whose RCU callbacks will be offloaded. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Allow rcu_nocbs= to specify all CPUsPaul E. McKenney2019-03-261-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, the rcu_nocbs= kernel boot parameter requires that a specific list of CPUs be specified, and has no way to say "all of them". As noted by user RavFX in a comment to Phoronix topic 1002538, this is an inconvenient side effect of the removal of the RCU_NOCB_CPU_ALL Kconfig option. This commit therefore enables the rcu_nocbs= kernel boot parameter to be given the string "all", as in "rcu_nocbs=all" to specify that all CPUs on the system are to have their RCU callbacks offloaded. Another approach would be to make cpulist_parse() check for "all", but there are uses of cpulist_parse() that do other checking, which could conflict with an "all". This commit therefore focuses on the specific use of cpulist_parse() in rcu_nocb_setup(). Just a note to other people who would like changes to Linux-kernel RCU: If you send your requests to me directly, they might get fixed somewhat faster. RavFX's comment was posted on January 22, 2018 and I first saw it on March 5, 2019. And the only reason that I found it -at- -all- was that I was looking for projects using RCU, and my search engine showed me that Phoronix comment quite by accident. Your choice, though! ;-) Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Move common code out of if-else blockAkira Yokosawa2019-03-261-3/+1Star
| | | | | | | | | | | | | | | | | | | | | | | | | | As the result of recent addition of "rdp->core_needs_qs = false;" in the "if" block, now both branches of the if-else have the same assignment. Factor it out and reduce line count. Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
| * rcu: Set rcutree.kthread_prio sysfs access to read-onlyLiu Song2019-03-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rcutree.kthread_prio kernel-boot parameter is used to set the priority for boost (rcub), per-CPU (rcuc), and grace-period (rcu_preempt or rcu_sched) kthreads. It is also used by rcutorture to check whether it is possible to meaningfully test RCU priority boosting. However, all of these cases will either ignore or be confused by any post-boot changes to rcutree.kthread_prio. Note that the user really can change the priorities of all of these kthreads using chrt, given sufficient privileges. Therefore, the read-write nature of sysfs access to rcutree.kthread_prio is thus at best an attractive nuisance. This commit therefore changes sysfs access to rcutree.kthread_prio to be read-only. Signed-off-by: Liu Song <liu.song11@zte.com.cn> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Make exit_rcu() handle non-preempted RCU readersPaul E. McKenney2019-03-261-7/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The purpose of exit_rcu() is to handle cases where buggy code causes a task to exit within an RCU read-side critical section. It currently does that in the case where said RCU read-side critical section was preempted at least once, but fails to handle cases where preemption did not occur. This case needs to be handled because otherwise the final context switch away from the exiting task will incorrectly behave as if task exit were instead a preemption of an RCU read-side critical section, and will therefore queue the exiting task. The exiting task will have exited, and thus won't ever execute rcu_read_unlock(), which means that it will remain queued forever, blocking all subsequent grace periods, and eventually resulting in OOM. Although this is arguably better than letting grace periods proceed and having a later rcu_read_unlock() access the now-freed task structure that once belonged to the exiting tasks, it would obviously be better to correctly handle this case. This commit therefore sets ->rcu_read_lock_nesting to 1 in that case, so that the subsequence call to __rcu_read_unlock() causes the exiting task to exit its dangling RCU read-side critical section. Note that deferred quiescent states need not be considered. The reason is that removing the task from the ->blkd_tasks[] list in the call to rcu_preempt_deferred_qs() handles the per-task component of any deferred quiescent state, and all other components of any deferred quiescent state are associated with the CPU, which isn't going anywhere until some later CPU-hotplug operation, which will report any remaining deferred quiescent states from within the rcu_report_dead() function. Note also that negative values of ->rcu_read_lock_nesting need not be considered. First, these won't show up in exit_rcu() unless there is a serious bug in RCU, and second, setting ->rcu_read_lock_nesting sets the state so that the RCU read-side critical section will be exited normally. Again, this code has no effect unless there has been some prior bug that prevents a task from leaving an RCU read-side critical section before exiting. Furthermore, there have been no reports of the bug fixed by this commit appearing in production. This commit is therefore absolutely -not- recommended for backporting to -stable. Reported-by: ABHISHEK DUBEY <dabhishek@iisc.ac.in> Reported-by: BHARATH Y MOURYA <bharathm@iisc.ac.in> Reported-by: Aravinda Prasad <aravinda@iisc.ac.in> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: ABHISHEK DUBEY <dabhishek@iisc.ac.in>
| * rcu: rcu_qs -- Use raise_softirq_irqoff to not save irqs twiceCyrill Gorcunov2019-03-261-1/+1
| | | | | | | | | | | | | | | | | | The rcu_qs is disabling IRQs by self so no need to do the same in raise_softirq but instead we can save some cycles using raise_softirq_irqoff directly. CC: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Avoid unnecessary softirq when system is idleJoel Fernandes (Google)2019-03-261-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When there are no callbacks pending on an idle system, I noticed that RCU softirq is continuously firing. During this the cpu_no_qs is set to false, and core_needs_qs is set to true indefinitely. This causes rcu_process_callbacks to be repeatedly called, even though the node corresponding to the CPU has that CPU's mask bit cleared and the system is idle. I believe the race is when such mask clearing is done during idle CPU scan of the quiescent state forcing stage in the kthread instead of the softirq. Since the rnp mask is cleared, but the flags on the CPU's rdp are not cleared, the CPU thinks it still needs to report to core RCU. Cure this by clearing the core_needs_qs flag when the CPU detects that its node is already updated which will avoid the unwanted softirq raises to the benefit of real-time systems. Test: Ran rcutorture for various tree RCU configs. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| * rcu: Unconditionally expedite during suspend/hibernatePaul E. McKenney2019-03-261-4/+2Star
|/ | | | | | | | | | | | | | | The rcu_pm_notify() function refuses to switch to/from expedited grace periods on systems with more than 256 CPUs due to the serialized initialization of expedited grace periods. However, expedited grace periods are now initialized in parallel, removing this concern. This commit therefore removes the checks from rcu_pm_notify(), so that expedited grace periods are used unconditionally during suspend/resume and hibernate/wake operations. As always, real-time workloads wishing to completely avoid expedited grace periods can use the rcupdate.rcu_normal= kernel parameter. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* Merge branch 'perf-core-for-linus' of ↵Linus Torvalds2019-03-062-0/+4
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull perf updates from Ingo Molnar: "Lots of tooling updates - too many to list, here's a few highlights: - Various subcommand updates to 'perf trace', 'perf report', 'perf record', 'perf annotate', 'perf script', 'perf test', etc. - CPU and NUMA topology and affinity handling improvements, - HW tracing and HW support updates: - Intel PT updates - ARM CoreSight updates - vendor HW event updates - BPF updates - Tons of infrastructure updates, both on the build system and the library support side - Documentation updates. - ... and lots of other changes, see the changelog for details. Kernel side updates: - Tighten up kprobes blacklist handling, reduce the number of places where developers can install a kprobe and hang/crash the system. - Fix/enhance vma address filter handling. - Various PMU driver updates, small fixes and additions. - refcount_t conversions - BPF updates - error code propagation enhancements - misc other changes" * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (238 commits) perf script python: Add Python3 support to syscall-counts-by-pid.py perf script python: Add Python3 support to syscall-counts.py perf script python: Add Python3 support to stat-cpi.py perf script python: Add Python3 support to stackcollapse.py perf script python: Add Python3 support to sctop.py perf script python: Add Python3 support to powerpc-hcalls.py perf script python: Add Python3 support to net_dropmonitor.py perf script python: Add Python3 support to mem-phys-addr.py perf script python: Add Python3 support to failed-syscalls-by-pid.py perf script python: Add Python3 support to netdev-times.py perf tools: Add perf_exe() helper to find perf binary perf script: Handle missing fields with -F +.. perf data: Add perf_data__open_dir_data function perf data: Add perf_data__(create_dir|close_dir) functions perf data: Fail check_backup in case of error perf data: Make check_backup work over directories perf tools: Add rm_rf_perf_data function perf tools: Add pattern name checking to rm_rf perf tools: Add depth checking to rm_rf perf data: Add global path holder ...
| * kprobes: Prohibit probing on RCU debug routineMasami Hiramatsu2019-02-131-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since kprobe itself depends on RCU, probing on RCU debug routine can cause recursive breakpoint bugs. Prohibit probing on RCU debug routines. int3 ->do_int3() ->ist_enter() ->RCU_LOCKDEP_WARN() ->debug_lockdep_rcu_enabled() -> int3 Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andrea Righi <righi.andrea@gmail.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/154998807741.31052.11229157537816341591.stgit@devbox Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()Masami Hiramatsu2019-02-131-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Prohibit probing on the functions called before kprobe_int3_handler() in do_int3(). More specifically, ftrace_int3_handler(), poke_int3_handler(), and ist_enter(). And since rcu_nmi_enter() is called by ist_enter(), it also should be marked as NOKPROBE_SYMBOL. Since those are handled before kprobe_int3_handler(), probing those functions can cause a breakpoint recursion and crash the kernel. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andrea Righi <righi.andrea@gmail.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/154998793571.31052.11301258949601150994.stgit@devbox Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds2019-03-0514-650/+390Star
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: "The main RCU related changes in this cycle were: - Additional cleanups after RCU flavor consolidation - Grace-period forward-progress cleanups and improvements - Documentation updates - Miscellaneous fixes - spin_is_locked() conversions to lockdep - SPDX changes to RCU source and header files - SRCU updates - Torture-test updates, including nolibc updates and moving nolibc to tools/include" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits) locking/locktorture: Convert to SPDX license identifier linux/torture: Convert to SPDX license identifier torture: Convert to SPDX license identifier linux/srcu: Convert to SPDX license identifier linux/rcutree: Convert to SPDX license identifier linux/rcutiny: Convert to SPDX license identifier linux/rcu_sync: Convert to SPDX license identifier linux/rcu_segcblist: Convert to SPDX license identifier linux/rcupdate: Convert to SPDX license identifier linux/rcu_node_tree: Convert to SPDX license identifier rcu/update: Convert to SPDX license identifier rcu/tree: Convert to SPDX license identifier rcu/tiny: Convert to SPDX license identifier rcu/sync: Convert to SPDX license identifier rcu/srcu: Convert to SPDX license identifier rcu/rcutorture: Convert to SPDX license identifier rcu/rcu_segcblist: Convert to SPDX license identifier rcu/rcuperf: Convert to SPDX license identifier rcu/rcu.h: Convert to SPDX license identifier RCU/torture.txt: Remove section MODULE PARAMETERS ...
| | \
| | \
| | \
| | \
| | \
| | \
| *-----. \ Merge branches 'doc.2019.01.26a', 'fixes.2019.01.26a', 'sil.2019.01.26a', ↵Paul E. McKenney2019-02-0914-300/+118Star
| |\ \ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'spdx.2019.02.09a', 'srcu.2019.01.26a' and 'torture.2019.01.26a' into HEAD doc.2019.01.26a: Documentation updates. fixes.2019.01.26a: Miscellaneous fixes. sil.2019.01.26a: Removal of a few more spin_is_locked() instances. spdx.2019.02.09a: Add SPDX identifiers to RCU files srcu.2019.01.26a: SRCU updates. torture.2019.01.26a: Torture-test updates.
| | | | | * | rcuperf: Stop abusing IS_ENABLED()Paul E. McKenney2019-01-261-1/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The ever-evolving IS_ENABLED() macro is intended for CONFIG_* Kconfig options, but rcuperf currently uses it for the decidedly non-CONFIG_* MODULE macro. In the spirit of not inviting trouble, this commit substitutes tried-and-true #ifdef. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Ingo Molnar <mingo@kernel.org>
| | | | | * | rcutorture: Add grace period after CPU offlinePaul E. McKenney2019-01-261-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Beyond a certain point in the CPU-hotplug offline process, timers get stranded on the outgoing CPU, and won't fire until that CPU comes back online, which might well be never. This commit therefore adds a hook in torture_onoff_init() that is invoked from torture_offline(), which rcutorture uses to occasionally wait for a grace period. This should result in failures for RCU implementations that rely on stranded timers eventually firing in the absence of the CPU coming back online. Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | | | * | rcutorture: Record grace periods in forward-progress histogramPaul E. McKenney2019-01-261-7/+22
| | |_|_|/ / | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit records grace periods in rcutorture's n_launders_hist[] histogram, thus allowing rcu_torture_fwd_cb_hist() to print out the elapsed number of grace periods between buckets. This information helps to determine whether a lack of forward progress is due to stalled grace periods on the one hand or due to sluggish callback invocation on the other. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | | * | srcu: Remove srcu_queue_delayed_work_on()Sebastian Andrzej Siewior2019-01-263-43/+24Star
| | |_|/ / | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | srcu_queue_delayed_work_on() disables preemption (and therefore CPU hotplug in RCU's case) and then checks based on its own accounting if a CPU is online. If the CPU is online it uses queue_delayed_work_on() otherwise it fallbacks to queue_delayed_work(). The problem here is that queue_work() on -RT does not work with disabled preemption. queue_work_on() works also on an offlined CPU. queue_delayed_work_on() has the problem that it is possible to program a timer on an offlined CPU. This timer will fire once the CPU is online again. But until then, the timer remains programmed and nothing will happen. Add a local timer which will fire (as requested per delay) on the local CPU and then enqueue the work on the specific CPU. RCUtorture testing with SRCU-P for 24h showed no problems. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
| | | * | rcu/update: Convert to SPDX license identifierPaul E. McKenney2019-02-091-15/+2Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
| | | * | rcu/tree: Convert to SPDX license identifierPaul E. McKenney2019-02-094-61/+9Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> [ paulmck: Update .h file SPDX comment format per Joe Perches. ] Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
| | | * | rcu/tiny: Convert to SPDX license identifierPaul E. McKenney2019-02-091-15/+2Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
| | | * | rcu/sync: Convert to SPDX license identifierPaul E. McKenney2019-02-091-14/+1Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
| | | * | rcu/srcu: Convert to SPDX license identifierPaul E. McKenney2019-02-092-30/+4Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
| | | * | rcu/rcutorture: Convert to SPDX license identifierPaul E. McKenney2019-02-091-16/+3Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
| | | * | rcu/rcu_segcblist: Convert to SPDX license identifierPaul E. McKenney2019-02-092-30/+4Star
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the license boiler plate with a SPDX license identifier. While in the area, update an email address. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
generated by cgit v1.2.3-55-g7522 (git 2.39.0) at 2024-11-14 08:05:44 +0100