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2016-05-19debugobjects: insulate non-fixup logic related to static obj from fixup ↵Du, Changbin-23/+3
callbacks When activating a static object we need make sure that the object is tracked in the object tracker. If it is a non-static object then the activation is illegal. In previous implementation, each subsystem need take care of this in their fixup callbacks. Actually we can put it into debugobjects core. Thus we can save duplicated code, and have *pure* fixup callbacks. To achieve this, a new callback "is_static_object" is introduced to let the type specific code decide whether a object is static or not. If yes, we take it into object tracker, otherwise give warning and invoke fixup callback. This change has paassed debugobjects selftest, and I also do some test with all debugobjects supports enabled. At last, I have a concern about the fixups that can it change the object which is in incorrect state on fixup? Because the 'addr' may not point to any valid object if a non-static object is not tracked. Then Change such object can overwrite someone's memory and cause unexpected behaviour. For example, the timer_fixup_activate bind timer to function stub_timer. Link: http://lkml.kernel.org/r/1462576157-14539-1-git-send-email-changbin.du@intel.com [changbin.du@intel.com: improve code comments where invoke the new is_static_object callback] Link: http://lkml.kernel.org/r/1462777431-8171-1-git-send-email-changbin.du@intel.com Signed-off-by: Du, Changbin <changbin.du@intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Triplett <josh@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tejun Heo <tj@kernel.org> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-19rcu: update debugobjects fixup callbacks return typeDu, Changbin-3/+3
Update the return type to use bool instead of int, corresponding to cheange (debugobjects: make fixup functions return bool instead of int). Signed-off-by: Du, Changbin <changbin.du@intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Triplett <josh@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tejun Heo <tj@kernel.org> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-31rcu: Remove superfluous versions of rcu_read_lock_sched_held()Boqun Feng-2/+2
Currently, we have four versions of rcu_read_lock_sched_held(), depending on the combined choices on PREEMPT_COUNT and DEBUG_LOCK_ALLOC. However, there is an existing function preemptible() that already distinguishes between the PREEMPT_COUNT=y and PREEMPT_COUNT=n cases, and allows these four implementations to be consolidated down to two. This commit therefore uses preemptible() to achieve this consolidation. Note that there could be a small performance regression in the case of CONFIG_DEBUG_LOCK_ALLOC=y && PREEMPT_COUNT=n. However, given the overhead associated with CONFIG_DEBUG_LOCK_ALLOC=y, this should be down in the noise. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-02-23rcu: Export rcu_gp_is_normal()Paul E. McKenney-0/+1
This commit exports rcu_gp_is_normal() in order to allow it to be used by rcutorture and rcuperf. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-07rcu: Remove TINY_RCU bloat from pointless boot parametersPaul E. McKenney-3/+4
The rcu_expedited, rcu_normal, and rcu_normal_after_boot kernel boot parameters are pointless in the case of TINY_RCU because in that case synchronous grace periods, both expedited and normal, are no-ops. However, these three symbols contribute several hundred bytes of bloat. This commit therefore uses CPP directives to avoid compiling this code in TINY_RCU kernels. Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-12-04rcu: Allow expedited grace periods to be disabled at initPaul E. McKenney-0/+5
Expedited grace periods can speed up boot, but are undesirable in aggressive real-time systems. This commit therefore introduces a kernel parameter rcupdate.rcu_normal_after_boot that disables expedited grace periods just before init is spawned. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-04rcu: Add rcu_normal kernel parameter to suppress expeditingPaul E. McKenney-0/+12
Although expedited grace periods can be quite useful, and although their OS jitter has been greatly reduced, they can still pose problems for extreme real-time workloads. This commit therefore adds a rcu_normal kernel boot parameter (which can also be manipulated via sysfs) to suppress expedited grace periods, that is, to treat requests for expedited grace periods as if they were requests for normal grace periods. If both rcu_expedited and rcu_normal are specified, rcu_normal wins. This means that if you are relying on expedited grace periods to speed up boot, you will want to specify rcu_expedited on the kernel command line, and then specify rcu_normal via sysfs once boot completes. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-10-06rcu: Use rcu_callback_t in call_rcu*() and friendsBoqun Feng-1/+1
As we now have rcu_callback_t typedefs as the type of rcu callbacks, we should use it in call_rcu*() and friends as the type of parameters. This could save us a few lines of code and make it clear which function requires an rcu callbacks rather than other callbacks as its argument. Besides, this can also help cscope to generate a better database for code reading. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-07-22rcu: Fix backwards RCU_LOCKDEP_WARN() in synchronize_rcu_tasks()Paul E. McKenney-1/+1
The RCU_LOCKDEP_WARN() in synchronize_rcu_tasks() triggers if the scheduler is active, which is backwards. This commit therefore negates the test. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-07-22rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()Paul E. McKenney-2/+2
This commit renames rcu_lockdep_assert() to RCU_LOCKDEP_WARN() for consistency with the WARN() series of macros. This also requires inverting the sense of the conditional, which this commit also does. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Ingo Molnar <mingo@kernel.org>
2015-07-22rcu: Create a synchronize_rcu_mult()Paul E. McKenney-10/+27
There have been several requests for a primitive that waits for grace periods for several RCU flavors concurrently, so this commit creates it. This is a variadic macro, and you pass in the call_rcu() functions of the flavors of RCU that you wish to wait for. Note that you cannot pass in call_srcu() for two reasons: (1) This would result in a type mismatch and (2) You need to specify which srcu_struct you want to use. Handle this by creating a wrapper function for your SRCU domain, for example: void call_srcu_mine(struct rcu_head *head, rcu_callback_t func) { call_srcu(&ss_mine, head, func); } You can then do something like this: synchronize_rcu_mult(call_srcu_mine, call_rcu, call_rcu_sched); Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-07-15rcu: Deinline rcu_read_lock_sched_held() if DEBUG_LOCK_ALLOCDenys Vlasenko-0/+49
DEBUG_LOCK_ALLOC=y is not a production setting, but it is not very unusual either. Many developers routinely use kernels built with it enabled. Apart from being selected by hand, it is also auto-selected by PROVE_LOCKING "Lock debugging: prove locking correctness" and LOCK_STAT "Lock usage statistics" config options. LOCK STAT is necessary for "perf lock" to work. I wouldn't spend too much time optimizing it, but this particular function has a very large cost in code size: when it is deinlined, code size decreases by 830,000 bytes: text data bss dec hex filename 85674192 22294776 20627456 128596424 7aa39c8 vmlinux.before 84837612 22294424 20627456 127759492 79d7484 vmlinux (with this config: http://busybox.net/~vda/kernel_config) Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> CC: Josh Triplett <josh@joshtriplett.org> CC: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> CC: Lai Jiangshan <laijs@cn.fujitsu.com> CC: Tejun Heo <tj@kernel.org> CC: Oleg Nesterov <oleg@redhat.com> CC: linux-kernel@vger.kernel.org Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-05-27rcu: Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()Paul E. McKenney-15/+15
This commit moves from the old ACCESS_ONCE() API to the new READ_ONCE() and WRITE_ONCE() APIs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Updated to include kernel/torture.c as suggested by Jason Low. ]
2015-03-20Merge branches 'doc.2015.02.26a', 'earlycb.2015.03.03a', ↵Paul E. McKenney-9/+63
'fixes.2015.03.03a', 'gpexp.2015.02.26a', 'hotplug.2015.03.20a', 'sysidle.2015.02.26b' and 'tiny.2015.02.26a' into HEAD doc.2015.02.26a: Documentation changes earlycb.2015.03.03a: Permit early-boot RCU callbacks fixes.2015.03.03a: Miscellaneous fixes gpexp.2015.02.26a: In-kernel expediting of normal grace periods hotplug.2015.03.20a: CPU hotplug fixes sysidle.2015.02.26b: NO_HZ_FULL_SYSIDLE fixes tiny.2015.02.26a: TINY_RCU fixes
2015-02-26rcu: Add Kconfig option to expedite grace periods during bootPaul E. McKenney-1/+10
This commit adds a CONFIG_RCU_EXPEDITE_BOOT Kconfig parameter that emulates a very early boot rcu_expedite_gp(). A late-boot call to rcu_end_inkernel_boot() will provide the corresponding rcu_unexpedite_gp(). The late-boot call to rcu_end_inkernel_boot() should be made just before init is spawned. According to Arjan: > To show the boot time, I'm using the timestamp of the "Write protecting" > line, that's pretty much the last thing we print prior to ring 3 execution. > > A kernel with default RCU behavior (inside KVM, only virtual devices) > looks like this: > > [ 0.038724] Write protecting the kernel read-only data: 10240k > > a kernel with expedited RCU (using the command line option, so that I > don't have to recompile between measurements and thus am completely > oranges-to-oranges) > > [ 0.031768] Write protecting the kernel read-only data: 10240k > > which, in percentage, is an 18% improvement. Reported-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Arjan van de Ven <arjan@linux.intel.com>
2015-02-26rcu: Provide rcu_expedite_gp() and rcu_unexpedite_gp()Paul E. McKenney-0/+48
Currently, expediting of normal synchronous grace-period primitives (synchronize_rcu() and friends) is controlled by the rcu_expedited() boot/sysfs parameter. This works well, but does not handle nesting. This commit therefore provides rcu_expedite_gp() to enable expediting and rcu_unexpedite_gp() to cancel a prior rcu_expedite_gp(), both of which support nesting. Reported-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-02-25rcu: Consolidate rcu_synchronize and wakeme_after_rcu()Paul E. McKenney-9/+6
There are currently duplicate identical definitions of the rcu_synchronize() structure and the wakeme_after_rcu() function. Thie commit therefore consolidates them. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-11-13Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', ↵Paul E. McKenney-2/+3
'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD cpu.2014.11.03a: Changes for per-CPU variables. doc.2014.11.13a: Documentation updates. fixes.2014.11.13a: Miscellaneous fixes. signal.2014.10.29a: Signal changes. rt.2014.10.29a: Real-time changes. torture.2014.11.03a: torture-test changes.
2014-11-13rcu: Fix FIXME in rcu_tasks_kthread()Paul E. McKenney-1/+2
This commit affines rcu_tasks_kthread() to the housekeeping CPUs in CONFIG_NO_HZ_FULL builds. This is just a default, so systems administrators are free to put this kthread somewhere else if they wish. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-11-03rcutorture: Add early boot self testsPranith Kumar-0/+84
Add early boot self tests for RCU under CONFIG_PROVE_RCU. Currently the only test is adding a dummy callback which increments a counter which we then later verify after calling rcu_barrier*(). Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-10-29rcu: Remove redundant TREE_PREEMPT_RCU config optionPranith Kumar-1/+1
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: Pranith Kumar <bobby.prani@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-16Merge branch 'rcu-tasks.2014.09.10a' into HEADPaul E. McKenney-1/+312
rcu-tasks.2014.09.10a: Add RCU-tasks flavor of RCU.
2014-09-07rcu: Remove local_irq_disable() in rcu_preempt_note_context_switch()Paul E. McKenney-1/+1
The rcu_preempt_note_context_switch() function is on a scheduling fast path, so it would be good to avoid disabling irqs. The reason that irqs are disabled is to synchronize process-level and irq-handler access to the task_struct ->rcu_read_unlock_special bitmask. This commit therefore makes ->rcu_read_unlock_special instead be a union of bools with a short allowing single-access checks in RCU's __rcu_read_unlock(). This results in the process-level and irq-handler accesses being simple loads and stores, so that irqs need no longer be disabled. This commit therefore removes the irq disabling from rcu_preempt_note_context_switch(). Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Additional information on RCU-tasks stall-warning messagesPaul E. McKenney-0/+9
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Make rcu_tasks_kthread()'s GP-wait loop allow preemptionPaul E. McKenney-5/+6
The grace-period-wait loop in rcu_tasks_kthread() is under (unnecessary) RCU protection, and therefore has no preemption points in a PREEMPT=n kernel. This commit therefore removes the RCU protection and inserts cond_resched(). Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Make TASKS_RCU handle nohz_full= CPUsPaul E. McKenney-1/+3
Currently TASKS_RCU would ignore a CPU running a task in nohz_full= usermode execution. There would be neither a context switch nor a scheduling-clock interrupt to tell TASKS_RCU that the task in question had passed through a quiescent state. The grace period would therefore extend indefinitely. This commit therefore makes RCU's dyntick-idle subsystem record the task_struct structure of the task that is running in dyntick-idle mode on each CPU. The TASKS_RCU grace period can then access this information and record a quiescent state on behalf of any CPU running in dyntick-idle usermode. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Defer rcu_tasks_kthread() creation till first call_rcu_tasks()Paul E. McKenney-7/+26
It is expected that many sites will have CONFIG_TASKS_RCU=y, but will never actually invoke call_rcu_tasks(). For such sites, creating rcu_tasks_kthread() at boot is wasteful. This commit therefore defers creation of this kthread until the time of the first call_rcu_tasks(). This of course means that the first call_rcu_tasks() must be invoked from process context after the scheduler is fully operational. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Improve RCU-tasks energy efficiencyPaul E. McKenney-2/+12
The current RCU-tasks implementation uses strict polling to detect callback arrivals. This works quite well, but is not so good for energy efficiency. This commit therefore replaces the strict polling with a wait queue. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Add stall-warning checks for RCU-tasksPaul E. McKenney-4/+25
This commit adds a ten-minute RCU-tasks stall warning. The actual time is controlled by the boot/sysfs parameter rcu_task_stall_timeout, with values less than or equal to zero disabling the stall warnings. The default value is ten minutes, which means that the tasks that have not yet responded will get their stacks dumped every ten minutes, until they pass through a voluntary context switch. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Export RCU-tasks APIs to GPL modulesSteven Rostedt-0/+2
This commit exports the RCU-tasks synchronous APIs, synchronize_rcu_tasks() and rcu_barrier_tasks(), to GPL-licensed kernel modules. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2014-09-07rcu: Make TASKS_RCU handle tasks that are almost done exitingPaul E. McKenney-0/+21
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 <oleg@redhat.com> Suggested-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Add synchronous grace-period waiting for RCU-tasksPaul E. McKenney-0/+55
It turns out to be easier to add the synchronous grace-period waiting functions to RCU-tasks than to work around their absense in rcutorture, so this commit adds them. The key point is that the existence of call_rcu_tasks() means that rcutorture needs an rcu_barrier_tasks(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Add call_rcu_tasks()Paul E. McKenney-0/+171
This commit adds a new RCU-tasks flavor of RCU, which provides call_rcu_tasks(). This RCU flavor's quiescent states are voluntary context switch (not preemption!) and userspace execution (not the idle loop -- use some sort of schedule_on_each_cpu() if you need to handle the idle tasks. Note that unlike other RCU flavors, these quiescent states occur in tasks, not necessarily CPUs. Includes fixes from Steven Rostedt. This RCU flavor is assumed to have very infrequent latency-tolerant updaters. This assumption permits significant simplifications, including a single global callback list protected by a single global lock, along with a single task-private linked list containing all tasks that have not yet passed through a quiescent state. If experience shows this assumption to be incorrect, the required additional complexity will be added. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-09-07rcu: Uninline rcu_read_lock_held()Oleg Nesterov-0/+32
This commit uninlines rcu_read_lock_held(). According to "size vmlinux" this saves 28549 in .text: - 5541731 3014560 14757888 23314179 + 5513182 3026848 14757888 23297918 Note: it looks as if the data grows by 12288 bytes but this is not true, it does not actually grow. But .data starts with ALIGN(THREAD_SIZE) and since .text shrinks the padding grows, and thus .data grows too as it seen by /bin/size. diff System.map: - ffffffff81510000 D _sdata - ffffffff81510000 D init_thread_union + ffffffff81509000 D _sdata + ffffffff8150c000 D init_thread_union Perhaps we can change vmlinux.lds.S to .data itself, so that /bin/size can't "wrongly" report that .data grows if .text shinks. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-07-09rcu: Remove CONFIG_PROVE_RCU_DELAYPaul E. McKenney-3/+0
The CONFIG_PROVE_RCU_DELAY Kconfig parameter doesn't appear to be very effective at finding race conditions, so this commit removes it. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Andi Kleen <ak@linux.intel.com> [ paulmck: Remove definition and uses as noted by Paul Bolle. ]
2014-06-23rcu: Reduce overhead of cond_resched() checks for RCUPaul E. McKenney-18/+0
Commit ac1bea85781e (Make cond_resched() report RCU quiescent states) fixed a problem where a CPU looping in the kernel with but one runnable task would give RCU CPU stall warnings, even if the in-kernel loop contained cond_resched() calls. Unfortunately, in so doing, it introduced performance regressions in Anton Blanchard's will-it-scale "open1" test. The problem appears to be not so much the increased cond_resched() path length as an increase in the rate at which grace periods complete, which increased per-update grace-period overhead. This commit takes a different approach to fixing this bug, mainly by moving the RCU-visible quiescent state from cond_resched() to rcu_note_context_switch(), and by further reducing the check to a simple non-zero test of a single per-CPU variable. However, this approach requires that the force-quiescent-state processing send resched IPIs to the offending CPUs. These will be sent only once the grace period has reached an age specified by the boot/sysfs parameter rcutree.jiffies_till_sched_qs, or once the grace period reaches an age halfway to the point at which RCU CPU stall warnings will be emitted, whichever comes first. Reported-by: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Christoph Lameter <cl@gentwo.org> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> [ paulmck: Made rcu_momentary_dyntick_idle() as suggested by the ktest build robot. Also fixed smp_mb() comment as noted by Oleg Nesterov. ] Merge with e552592e (Reduce overhead of cond_resched() checks for RCU) Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-06-23rcu: Export debug_init_rcu_head() and and debug_init_rcu_head()Paul E. McKenney-2/+2
Currently, call_rcu() relies on implicit allocation and initialization for the debug-objects handling of RCU callbacks. If you hammer the kernel hard enough with Sasha's modified version of trinity, you can end up with the sl*b allocators recursing into themselves via this implicit call_rcu() allocation. This commit therefore exports the debug_init_rcu_head() and debug_rcu_head_free() functions, which permits the allocators to allocated and pre-initialize the debug-objects information, so that there no longer any need for call_rcu() to do that initialization, which in turn prevents the recursion into the memory allocators. Reported-by: Sasha Levin <sasha.levin@oracle.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Looks-good-to: Christoph Lameter <cl@linux.com>
2014-05-19rcu: Provide API to suppress stall warnings while sysrc runsRik van Riel-0/+12
Some sysrq handlers can run for a long time, because they dump a lot of data onto a serial console. Having RCU stall warnings pop up in the middle of them only makes the problem worse. This commit provides rcu_sysrq_start() and rcu_sysrq_end() APIs to temporarily suppress RCU CPU stall warnings while a sysrq request is handled. Signed-off-by: Rik van Riel <riel@redhat.com> [ paulmck: Fix TINY_RCU build error. ] Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-05-14sched,rcu: Make cond_resched() report RCU quiescent statesPaul E. McKenney-0/+18
Given a CPU running a loop containing cond_resched(), with no other tasks runnable on that CPU, RCU will eventually report RCU CPU stall warnings due to lack of quiescent states. Fortunately, every call to cond_resched() is a perfectly good quiescent state. Unfortunately, invoking rcu_note_context_switch() is a bit heavyweight for cond_resched(), especially given the need to disable preemption, and, for RCU-preempt, interrupts as well. This commit therefore maintains a per-CPU counter that causes cond_resched(), cond_resched_lock(), and cond_resched_softirq() to call rcu_note_context_switch(), but only about once per 256 invocations. This ratio was chosen in keeping with the relative time constants of RCU grace periods. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2014-02-26rcu: Ensure kernel/rcu/rcu.h can be sourced/used stand-alonePaul Gortmaker-1/+0
The kbuild test bot uncovered an implicit dependence on the trace header being present before rcu.h in ia64 allmodconfig that looks like this: In file included from kernel/ksysfs.c:22:0: kernel/rcu/rcu.h: In function '__rcu_reclaim': kernel/rcu/rcu.h:107:3: error: implicit declaration of function 'trace_rcu_invoke_kfree_callback' [-Werror=implicit-function-declaration] kernel/rcu/rcu.h:112:3: error: implicit declaration of function 'trace_rcu_invoke_callback' [-Werror=implicit-function-declaration] cc1: some warnings being treated as errors Looking at other rcu.h users, we can find that they all were sourcing the trace header in advance of rcu.h itself, as seen in the context of this diff. There were also some inconsistencies as to whether it was or wasn't sourced based on the parent tracing Kconfig. Rather than "fix" it at each use site, and have inconsistent use based on whether "#ifdef CONFIG_RCU_TRACE" was used or not, lets just source the trace header just once, in the actual consumer of it, which is rcu.h itself. We include it unconditionally, as build testing shows us that is a hard requirement for some files. Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2014-02-17rcu: Stop tracking FSF's postal addressPaul E. McKenney-2/+2
All of the RCU source files have the usual GPL header, which contains a long-obsolete postal address for FSF. To avoid the need to track the FSF office's movements, this commit substitutes the URL where GPL may be found. Reported-by: Greg KH <gregkh@linuxfoundation.org> Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2014-01-28Merge branch 'for-linus' of ↵Linus Torvalds-11/+0
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs updates from Al Viro: "Assorted stuff; the biggest pile here is Christoph's ACL series. Plus assorted cleanups and fixes all over the place... There will be another pile later this week" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (43 commits) __dentry_path() fixes vfs: Remove second variable named error in __dentry_path vfs: Is mounted should be testing mnt_ns for NULL or error. Fix race when checking i_size on direct i/o read hfsplus: remove can_set_xattr nfsd: use get_acl and ->set_acl fs: remove generic_acl nfs: use generic posix ACL infrastructure for v3 Posix ACLs gfs2: use generic posix ACL infrastructure jfs: use generic posix ACL infrastructure xfs: use generic posix ACL infrastructure reiserfs: use generic posix ACL infrastructure ocfs2: use generic posix ACL infrastructure jffs2: use generic posix ACL infrastructure hfsplus: use generic posix ACL infrastructure f2fs: use generic posix ACL infrastructure ext2/3/4: use generic posix ACL infrastructure btrfs: use generic posix ACL infrastructure fs: make posix_acl_create more useful fs: make posix_acl_chmod more useful ...
2014-01-25introduce __fcheck_files() to fix rcu_dereference_check_fdtable(), kill ↵Oleg Nesterov-11/+0
rcu_my_thread_group_empty() rcu_dereference_check_fdtable() looks very wrong, 1. rcu_my_thread_group_empty() was added by 844b9a8707f1 "vfs: fix RCU-lockdep false positive due to /proc" but it doesn't really fix the problem. A CLONE_THREAD (without CLONE_FILES) task can hit the same race with get_files_struct(). And otoh rcu_my_thread_group_empty() can suppress the correct warning if the caller is the CLONE_FILES (without CLONE_THREAD) task. 2. files->count == 1 check is not really right too. Even if this files_struct is not shared it is not safe to access it lockless unless the caller is the owner. Otoh, this check is sub-optimal. files->count == 0 always means it is safe to use it lockless even if files != current->files, but put_files_struct() has to take rcu_read_lock(). See the next patch. This patch removes the buggy checks and turns fcheck_files() into __fcheck_files() which uses rcu_dereference_raw(), the "unshared" callers, fget_light() and fget_raw_light(), can use it to avoid the warning from RCU-lockdep. fcheck_files() is trivially reimplemented as rcu_lockdep_assert() plus __fcheck_files(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-12-09rcu: Provide better diagnostics for blocking in RCU callback functionsPaul E. McKenney-0/+5
Currently blocking in an RCU callback function will result in "scheduling while atomic", which could be triggered for any number of reasons. To aid debugging, this patch introduces a rcu_callback_map that is used to tie the inappropriate voluntary context switch back to the fact that the function is being invoked from within a callback. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2013-10-15rcu: Move RCU-related source code to kernel/rcu directoryPaul E. McKenney-0/+347
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Ingo Molnar <mingo@kernel.org>