summaryrefslogtreecommitdiffstats
path: root/kernel/rcupreempt.c
Commit message (Collapse)AuthorAgeFilesLines
* Merge branch 'linus' into cpus4096Ingo Molnar2008-07-161-59/+379
|\ | | | | | | | | | | | | | | | | | | Conflicts: arch/x86/xen/smp.c kernel/sched_rt.c net/iucv/iucv.c Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * Merge branch 'core/rcu' into core/rcu-for-linusIngo Molnar2008-07-151-47/+371
| |\
| | * Merge branch 'linus' into core/rcuIngo Molnar2008-07-111-13/+9
| | |\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Conflicts: include/linux/rculist.h kernel/rcupreempt.c Signed-off-by: Ingo Molnar <mingo@elte.hu>
| | * | rcu: remove unused field struct rcu_data::rcu_taskletLai Jiangshan2008-06-161-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Since softirq works for rcu reclaimer, rcu_tasklet is unused now. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| | * | rcu: remove duplicated include in kernel/rcupreempt.cHuang Weiyi2008-05-191-1/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Removed duplicated include file <linux/rcupdate.h> in kernel/rcupreempt.c. Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| | * | rcu: fix rcu_try_flip_waitack_needed() to prevent grace-period stallPaul E. McKenney2008-05-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The comment was correct -- need to make the code match the comment. Without this patch, if a CPU goes dynticks idle (and stays there forever) in just the right phase of preemptible-RCU grace-period processing, grace periods stall. The offending sequence of events (courtesy of Promela/spin, at least after I got the liveness criterion coded correctly...) is as follows: o CPU 0 is in dynticks-idle mode. Its dynticks_progress_counter is (say) 10. o CPU 0 takes an interrupt, so rcu_irq_enter() increments CPU 0's dynticks_progress_counter to 11. o CPU 1 is doing RCU grace-period processing in rcu_try_flip_idle(), sees rcu_pending(), so invokes dyntick_save_progress_counter(), which in turn takes a snapshot of CPU 0's dynticks_progress_counter into CPU 0's rcu_dyntick_snapshot -- now set to 11. CPU 1 then updates the RCU grace-period state to rcu_try_flip_waitack(). o CPU 0 returns from its interrupt, so rcu_irq_exit() increments CPU 0's dynticks_progress_counter to 12. o CPU 1 later invokes rcu_try_flip_waitack(), which notices that CPU 0 has not yet responded, and hence in turn invokes rcu_try_flip_waitack_needed(). This function examines the state of CPU 0's dynticks_progress_counter and rcu_dyntick_snapshot variables, which it copies to curr (== 12) and snap (== 11), respectively. Because curr!=snap, the first condition fails. Because curr-snap is only 1 and snap is odd, the second condition fails. rcu_try_flip_waitack_needed() therefore incorrectly concludes that it must wait for CPU 0 to explicitly acknowledge the counter flip. o CPU 0 remains forever in dynticks-idle mode, never taking any more hardware interrupts or any NMIs, and never running any more tasks. (Of course, -something- will usually eventually happen, which might be why we haven't seen this one in the wild. Still should be fixed!) Therefore the grace period never ends. Fix is to make the code match the comment, as shown below. With this fix, the above scenario would be satisfied with curr being even, and allow the grace period to proceed. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Josh Triplett <josh@kernel.org> Cc: Dipankar Sarma <dipankar@in.ibm.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| | * | rcu: add call_rcu_sched()Paul E. McKenney2008-05-191-44/+370
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fourth cut of patch to provide the call_rcu_sched(). This is again to synchronize_sched() as call_rcu() is to synchronize_rcu(). Should be fine for experimental and -rt use, but not ready for inclusion. With some luck, I will be able to tell Andrew to come out of hiding on the next round. Passes multi-day rcutorture sessions with concurrent CPU hotplugging. Fixes since the first version include a bug that could result in indefinite blocking (spotted by Gautham Shenoy), better resiliency against CPU-hotplug operations, and other minor fixes. Fixes since the second version include reworking grace-period detection to avoid deadlocks that could happen when running concurrently with CPU hotplug, adding Mathieu's fix to avoid the softlockup messages, as well as Mathieu's fix to allow use earlier in boot. Fixes since the third version include a wrong-CPU bug spotted by Andrew, getting rid of the obsolete synchronize_kernel API that somehow snuck back in, merging spin_unlock() and local_irq_restore() in a few places, commenting the code that checks for quiescent states based on interrupting from user-mode execution or the idle loop, removing some inline attributes, and some code-style changes. Known/suspected shortcomings: o I still do not entirely trust the sleep/wakeup logic. Next step will be to use a private snapshot of the CPU online mask in rcu_sched_grace_period() -- if the CPU wasn't there at the start of the grace period, we don't need to hear from it. And the bit about accounting for changes in online CPUs inside of rcu_sched_grace_period() is ugly anyway. o It might be good for rcu_sched_grace_period() to invoke resched_cpu() when a given CPU wasn't responding quickly, but resched_cpu() is declared static... This patch also fixes a long-standing bug in the earlier preemptable-RCU implementation of synchronize_rcu() that could result in loss of concurrent external changes to a task's CPU affinity mask. I still cannot remember who reported this... Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| | * | rcupreempt: remove duplicate prototypesSteven Rostedt2008-05-191-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | rcu_batches_completed and rcu_patches_completed_bh are both declared in rcuclassic.h and rcupreempt.h. This patch removes the extra prototypes for them from rcupdate.h. rcu_batches_completed_bh is defined as a static inline in the rcupreempt.h header file. Trying to export this as EXPORT_SYMBOL_GPL causes linking problems with the powerpc linker. There's no need to export a static inlined function. Modules must be compiled with the same type of RCU implementation as the kernel they are for. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | | Merge branch 'core/softirq' of ↵Linus Torvalds2008-07-141-1/+1
| |\ \ \ | | |_|/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core/softirq' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: softirq: remove irqs_disabled warning from local_bh_enable softirq: remove initialization of static per-cpu variable Remove argument from open_softirq which is always NULL
| | * | Merge branch 'linus' into core/softirqIngo Molnar2008-06-231-2/+0
| | |\ \
| | * | | Remove argument from open_softirq which is always NULLCarlos R. Mafra2008-05-251-1/+1
| | | |/ | | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | As git-grep shows, open_softirq() is always called with the last argument being NULL block/blk-core.c: open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL); kernel/hrtimer.c: open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL); kernel/rcuclassic.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); kernel/rcupreempt.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL); kernel/sched.c: open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL); kernel/softirq.c: open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL); kernel/softirq.c: open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL); kernel/timer.c: open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL); net/core/dev.c: open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL); net/core/dev.c: open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL); This observation has already been made by Matthew Wilcox in June 2002 (http://www.cs.helsinki.fi/linux/linux-kernel/2002-25/0687.html) "I notice that none of the current softirq routines use the data element passed to them." and the situation hasn't changed since them. So it appears we can safely remove that extra argument to save 128 (54) bytes of kernel data (text). Signed-off-by: Carlos R. Mafra <crmafra@ift.unesp.br> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * | | Fix PREEMPT_RCU without HOTPLUG_CPUNick Piggin2008-07-101-12/+8
| | |/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | PREEMPT_RCU without HOTPLUG_CPU is broken. The rcu_online_cpu is called to initially populate rcu_cpu_online_map with all online CPUs when the hotplug event handler is installed, and also to populate the map with CPUs as they come online. The former case is meant to happen with and without HOTPLUG_CPU, but without HOTPLUG_CPU, the rcu_offline_cpu function is no-oped -- while it still gets called, it does not set the rcu CPU map. With a blank RCU CPU map, grace periods get to tick by completely oblivious to active RCU read side critical sections. This results in free-before-grace bugs. Fix is obvious once the problem is known. (Also, change __devinit to __cpuinit so the function gets thrown away on !HOTPLUG_CPU kernels). Signed-off-by: Nick Piggin <npiggin@suse.de> Reported-and-tested-by: Alexey Dobriyan <adobriyan@gmail.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ Nick is my personal hero of the day - Linus ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | | Merge commit 'v2.6.26-rc9' into cpus4096Ingo Molnar2008-07-061-2/+0
|\ \ \ | |/ /
| * | rcupreempt: remove export of rcu_batches_completed_bhSteven Rostedt2008-06-191-2/+0
| |/ | | | | | | | | | | | | | | | | | | | | | | In rcupreempt, rcu_batches_completed_bh is defined as a static inline in the header file. This does not need to be exported, and not only that, this breaks my PPC build. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: paulus@samba.org Cc: linuxppc-dev@ozlabs.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | core: use performance variant for_each_cpu_mask_nrMike Travis2008-05-231-5/+5
|/ | | | | | | | | | | | Change references from for_each_cpu_mask to for_each_cpu_mask_nr where appropriate Reviewed-by: Paul Jackson <pj@sgi.com> Reviewed-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Mike Travis <travis@sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* generic: reduce stack pressure in sched_affinityMike Travis2008-04-191-2/+2
| | | | | | | | | | | | | | | * Modify sched_affinity functions to pass cpumask_t variables by reference instead of by value. * Use new set_cpus_allowed_ptr function. Depends on: [sched-devel]: sched: add new set_cpus_allowed_ptr function Cc: Paul Jackson <pj@sgi.com> Cc: Cliff Wickman <cpw@sgi.com> Signed-off-by: Mike Travis <travis@sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rcupreempt: remove never-migrates assumption from rcu_process_callbacks()Paul E. McKenney2008-02-291-2/+4
| | | | | | | | | | | | | | | This patch fixes a potentially invalid access to a per-CPU variable in rcu_process_callbacks(). This per-CPU access needs to be done in such a way as to guarantee that the code using it cannot move to some other CPU before all uses of the value accessed have completed. Even though this code is currently only invoked from softirq context, which currrently cannot migrate to some other CPU, life would be better if this code did not silently make such an assumption. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rcupreempt: fix hibernate/resume in presence of PREEMPT_RCU and hotplugPaul E. McKenney2008-02-291-1/+2
| | | | | | | | | | | | | | | This fixes a oops encountered when doing hibernate/resume in presence of PREEMPT_RCU. The problem was that the code failed to disable preemption when accessing a per-CPU variable. This is OK when called from code that already has preemption disabled, but such is not the case from the suspend/resume code path. Reported-by: Dave Young <hidave.darkstar@gmail.com> Tested-by: Dave Young <hidave.darkstar@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* rcu: add support for dynamic ticks and preempt rcuSteven Rostedt2008-02-291-4/+220
| | | | | | | | | | | | | | | The PREEMPT-RCU can get stuck if a CPU goes idle and NO_HZ is set. The idle CPU will not progress the RCU through its grace period and a synchronize_rcu my get stuck. Without this patch I have a box that will not boot when PREEMPT_RCU and NO_HZ are set. That same box boots fine with this patch. This patch comes from the -rt kernel where it has been tested for several months. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Preempt-RCU: CPU Hotplug handlingPaul E. McKenney2008-01-251-5/+142
| | | | | | | | | | | This patch allows preemptible RCU to tolerate CPU-hotplug operations. It accomplishes this by maintaining a local copy of a map of online CPUs, which it accesses under its own lock. Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Preempt-RCU: implementationPaul E. McKenney2008-01-251-0/+816
This patch implements a new version of RCU which allows its read-side critical sections to be preempted. It uses a set of counter pairs to keep track of the read-side critical sections and flips them when all tasks exit read-side critical section. The details of this implementation can be found in this paper - http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf and the article- http://lwn.net/Articles/253651/ This patch was developed as a part of the -rt kernel development and meant to provide better latencies when read-side critical sections of RCU don't disable preemption. As a consequence of keeping track of RCU readers, the readers have a slight overhead (optimizations in the paper). This implementation co-exists with the "classic" RCU implementations and can be switched to at compiler. Also includes RCU tracing summarized in debugfs. [ akpm@linux-foundation.org: build fixes on non-preempt architectures ] Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Reviewed-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
OpenPOWER on IntegriCloud