- 26 Sep, 2012 1 commit
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Frederic Weisbecker authored
RCU currently insists that only idle tasks can enter RCU idle mode, which prohibits an adaptive tickless kernel (AKA nohz cpusets), which in turn would mean that usermode execution would always take scheduling-clock interrupts, even when there is only one task runnable on the CPU in question. This commit therefore adds rcu_user_enter() and rcu_user_exit(), which allow non-idle tasks to enter RCU idle mode. These are quite similar to rcu_idle_enter() and rcu_idle_exit(), respectively, except that they omit the idle-task checks. [ Updated to use "user" flag rather than separate check functions. ] [ paulmck: Updated to drop exports of new functions based on Josh's patch getting rid of the need for them. ] Signed-off-by:
Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Alessio Igor Bogani <abogani@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Avi Kivity <avi@redhat.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@ti.com> Cc: Max Krasnyansky <maxk@qualcomm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Reviewed-by:
Josh Triplett <josh@joshtriplett.org>
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- 25 Sep, 2012 4 commits
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Paul E. McKenney authored
Resolved conflict in kernel/sched/core.c using Peter Zijlstra's approach from https://lkml.org/lkml/2012/9/5/585.
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Paul E. McKenney authored
The conflicts between kernel/rcutree.h and kernel/rcutree_plugin.h were due to adjacent insertions and deletions, which were resolved by simply accepting the changes on both branches.
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Ingo Molnar authored
Merge Linux 3.6-rc7, to pick up fixes and to resolve a conflict in an upcoming pull. Signed-off-by:Ingo Molnar <mingo@kernel.org>
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Paul E. McKenney authored
Merge branches 'bigrt.2012.09.23a', 'doctorture.2012.09.23a', 'fixes.2012.09.23a', 'hotplug.2012.09.23a' and 'idlechop.2012.09.23a' into HEAD bigrt.2012.09.23a contains additional commits to reduce scheduling latency from RCU on huge systems (many hundrends or thousands of CPUs). doctorture.2012.09.23a contains documentation changes and rcutorture fixes. fixes.2012.09.23a contains miscellaneous fixes. hotplug.2012.09.23a contains CPU-hotplug-related changes. idle.2012.09.23a fixes architectures for which RCU no longer considered the idle loop to be a quiescent state due to earlier adaptive-dynticks changes. Affected architectures are alpha, cris, frv, h8300, m32r, m68k, mn10300, parisc, score, xtensa, and ia64.
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- 24 Sep, 2012 1 commit
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Linus Torvalds authored
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- 23 Sep, 2012 34 commits
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git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuildLinus Torvalds authored
Pull kbuild fixes from Michal Marek: "There are two more kbuild fixes for 3.6. One fixes a race between x86's archscripts target and the rule (re)building scripts/basic/fixdep. The second is a fix for the previous attempt at fixing make firmware_install with make 3.82. This new solution should work with any version of GNU make" * 'rc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild: x86/kbuild: archscripts depends on scripts_basic firmware: fix directory creation rule matching with make 3.80
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git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/stagingLinus Torvalds authored
Pull hwmon subsystem fixes from Jean Delvare. * 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging: hwmon: (fam15h_power) Tweak runavg_range on resume hwmon: (coretemp) Use get_online_cpus to avoid races involving CPU hotplug hwmon: (via-cputemp) Use get_online_cpus to avoid races involving CPU hotplug
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git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsiLinus Torvalds authored
Pull SCSI fixes from James Bottomley: "This is a set of four essential fixes: two oops related (bnx2i, virtio-scsi), one data corruption related (hpsa) and one failure to boot due to interrupt routing issues (mpt2ss). Signed-off-by: James Bottomley <JBottomley@Parallels.com>" * tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: [SCSI] hpsa: fix handling of protocol error [SCSI] mpt2sas: Fix for issue - Unable to boot from the drive connected to HBA [SCSI] bnx2i: Fixed NULL ptr deference for 1G bnx2 Linux iSCSI offload [SCSI] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list
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Shaun Ruffell authored
Fix potential NULL pointer dereference in edac_unregister_sysfs() on system boot introduced in 3.6-rc1. Since commit 7a623c03 ("edac: rewrite the sysfs code to use struct device") edac_mc_alloc() no longer initializes embedded kobjects in struct mem_ctl_info. Therefore edac_mc_free() can no longer simply decrement a kobject reference count to free the allocated memory unless the memory controller driver module had also called edac_mc_add_mc(). Now edac_mc_free() will check if the newly embedded struct device has been registered with sysfs before using either the standard device release functions or freeing the data structures itself with logic pulled out of the error path of edac_mc_alloc(). The BUG this patch resolves for me: BUG: unable to handle kernel NULL pointer dereference at (null) EIP is at __wake_up_common+0x1a/0x6a Process modprobe (pid: 933, ti=f3dc6000 task=f3db9520 task.ti=f3dc6000) Call Trace: complete_all+0x3f/0x50 device_pm_remove+0x23/0xa2 device_del+0x34/0x142 edac_unregister_sysfs+0x3b/0x5c [edac_core] edac_mc_free+0x29/0x2f [edac_core] e7xxx_probe1+0x268/0x311 [e7xxx_edac] e7xxx_init_one+0x56/0x61 [e7xxx_edac] local_pci_probe+0x13/0x15 ... Cc: Mauro Carvalho Chehab <mchehab@redhat.com> Cc: Shaohui Xie <Shaohui.Xie@freescale.com> Signed-off-by:
Shaun Ruffell <sruffell@digium.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Fengguang Wu authored
coccinelle warns about: + drivers/edac/edac_mc.c:429:9-23: ERROR: reference preceded by free on line 429 421 if (mci->csrows) { > 422 for (chn = 0; chn < tot_channels; chn++) { 423 csr = mci->csrows[chn]; 424 if (csr) { > 425 for (chn = 0; chn < tot_channels; chn++) 426 kfree(csr->channels[chn]); 427 kfree(csr); 428 } > 429 kfree(mci->csrows[i]); 430 } 431 kfree(mci->csrows); 432 } and that code block seem to mess things up in several ways (double free, memory leak, out-of-bound reads etc.): L422: The iterator "chn" and bound "tot_channels" are totally wrong. Should be "row" and "tot_csrows" respectively. Which means either memory leak, or out-of-bound reads (which if does not trigger an immediate page fault error, will further lead to kfree() on random addresses). L425: The inner loop is reusing the same iterator "chn" as the outer loop, which could lead to premature end of the outer loop, and hence memory leak. L429: The array index 'i' in mci->csrows[i] is a temporary value used in previous loops, and won't change at all in the current loop. Which means either out-of-bound read and possibly kfree(random number), or the same mci->csrows[i] get freed once and again, and possibly double free for the kfree(csr) in L427. L426/L427: a kfree(csr->channels) is needed in between to avoid leaking the memory. The buggy code was introduced by commit de3910eb ("edac: change the mem allocation scheme to make Documentation/kobject.txt happy") in the 3.6-rc1 merge window. Fix it by freeing up resources in this order: free csrows[i]->channels[j] free csrows[i]->channels free csrows[i] free csrows CC: Mauro Carvalho Chehab <mchehab@redhat.com> CC: Shaun Ruffell <sruffell@digium.com> Signed-off-by:Fengguang Wu <fengguang.wu@intel.com> Signed-off-by:
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Andreas Herrmann authored
The quirk introduced with commit 00250ec9 (hwmon: fam15h_power: fix bogus values with current BIOSes) is not only required during driver load but also when system resumes from suspend. The BIOS might set the previously recommended (but unsuitable) initilization value for the running average range register during resume. Signed-off-by:
Andreas Herrmann <andreas.herrmann3@amd.com> Tested-by:
Andreas Hartmann <andihartmann@01019freenet.de> Signed-off-by:
Jean Delvare <khali@linux-fr.org> Cc: stable@vger.kernel.org # 3.0+
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Silas Boyd-Wickizer authored
coretemp_init loops with for_each_online_cpu, adding platform_devices and sysfs interfaces, then calls register_hotcpu_notifier. There is a race if a CPU is offlined or onlined after the loop, but before register_hotcpu_notifier. The race might result in the absence of a platform_device+sysfs interface for an online CPU, or the presence of a platform_device+sysfs interface for an offline CPU. A similar race occurs during coretemp_exit, after the module calls unregister_hotcpu_notifier, but before it unregisters all devices, a CPU might offline and a device for an offline CPU will exist for a short while. This fix surrounds for_each_online_cpu and register_hotcpu_notifier with get_online_cpus+put_online_cpus; and surrounds unregister_hotcpu_notifier and device unregistering with get_online_cpus+put_online_cpus. Build tested. Signed-off-by:
Silas Boyd-Wickizer <sbw@mit.edu> Signed-off-by:
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Silas Boyd-Wickizer authored
via_cputemp_init loops with for_each_online_cpu, adding platform_devices, then calls register_hotcpu_notifier. If a CPU is offlined between the loop and register_hotcpu_notifier, then later onlined, via_cputemp_device_add will attempt to add platform devices with the same ID. A similar race occurs during via_cputemp_exit, after the module calls unregister_hotcpu_notifier, a CPU might offline and a device will exist for a CPU that is offline. This fix surrounds for_each_online_cpu and register_hotcpu_notifier with get_online_cpus+put_online_cpus; and surrounds unregister_hotcpu_notifier and device unregistering with get_online_cpus+put_online_cpus. Build tested. Signed-off-by:
Harald Welte <laforge@gnumonks.org> Signed-off-by:
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Paul E. McKenney authored
Traditionally, the entire idle task served as an RCU quiescent state. But when RCU read side critical sections started appearing within the idle loop, this traditional strategy became untenable. The fix was to create new RCU APIs named rcu_idle_enter() and rcu_idle_exit(), which must be called by each architecture's idle loop so that RCU can tell when it is safe to ignore a given idle CPU. Unfortunately, this fix was never applied to ia64, a shortcoming remedied by this commit. Reported by: Tony Luck <tony.luck@intel.com> Signed-off-by:
Paul E. McKenney <paul.mckenney@linaro.org> Cc: <stable@vger.kernel.org> # 3.3+ Signed-off-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the xtensa's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in scores's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the parisc's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the mn10300's idle loop. Reported-by:
David Howells <dhowells@redhat.com> Reviewed-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the m68k's idle loop. Reported-by:
Geert Uytterhoeven <geert@linux-m68k.org> Cc: m68k <linux-m68k@lists.linux-m68k.org> Cc: <stable@vger.kernel.org> # 3.3+ Signed-off-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the m32r's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the h8300's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the Frv's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the Cris's idle loop. Reported-by:
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Frederic Weisbecker authored
In the old times, the whole idle task was considered as an RCU quiescent state. But as RCU became more and more successful overtime, some RCU read side critical section have been added even in the code of some architectures idle tasks, for tracing for example. So nowadays, rcu_idle_enter() and rcu_idle_exit() must be called by the architecture to tell RCU about the part in the idle loop that doesn't make use of rcu read side critical sections, typically the part that puts the CPU in low power mode. This is necessary for RCU to find the quiescent states in idle in order to complete grace periods. Add this missing pair of calls in the Alpha's idle loop. Reported-by:
Michael Cree <mcree@orcon.net.nz> Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Matt Turner <mattst88@gmail.com> Cc: alpha <linux-alpha@vger.kernel.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: <stable@vger.kernel.org> # 3.3+ Reviewed-by:
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Frederic Weisbecker authored
cpu_idle() is called on the boot CPU by the init code with preemption disabled. But the cpu_idle() function in alpha doesn't handle this when it calls schedule() directly. Fix it by converting it into schedule_preempt_disabled(). Also disable preemption before calling cpu_idle() from secondary CPU entry code to stay consistent with this state. Signed-off-by:
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Silas Boyd-Wickizer authored
If arch/x86/kernel/cpuid.c is a module, a CPU might offline or online between the for_each_online_cpu() loop and the call to register_hotcpu_notifier in cpuid_init or the call to unregister_hotcpu_notifier in cpuid_exit. The potential races can lead to leaks/duplicates, attempts to destroy non-existant devices, or random pointer dereferences. For example, in cpuid_exit if: for_each_online_cpu(cpu) cpuid_device_destroy(cpu); class_destroy(cpuid_class); __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); <----- CPU onlines unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); the hotcpu notifier will attempt to create a device for the cpuid_class, which the module already destroyed. This fix surrounds for_each_online_cpu and register_hotcpu_notifier or unregister_hotcpu_notifier with get_online_cpus+put_online_cpus. Tested on a VM. Signed-off-by: -
Silas Boyd-Wickizer authored
If arch/x86/kernel/msr.c is a module, a CPU might offline or online between the for_each_online_cpu(i) loop and the call to register_hotcpu_notifier in msr_init or the call to unregister_hotcpu_notifier in msr_exit. The potential races can lead to leaks/duplicates, attempts to destroy non-existant devices, or random pointer dereferences. For example, in msr_init if: for_each_online_cpu(i) { err = msr_device_create(i); if (err != 0) goto out_class; } <----- CPU offlines register_hotcpu_notifier(&msr_class_cpu_notifier); and the CPU never onlines before msr_exit, then the module will never call msr_device_destroy for the associated CPU. This fix surrounds for_each_online_cpu and register_hotcpu_notifier or unregister_hotcpu_notifier with get_online_cpus+put_online_cpus. Tested on a VM. Signed-off-by: -
Peter Zijlstra authored
Rabik and Paul reported two different issues related to the same few lines of code. Rabik's issue is that the nr_uninterruptible migration code is wrong in that he sees artifacts due to this (Rabik please do expand in more detail). Paul's issue is that this code as it stands relies on us using stop_machine() for unplug, we all would like to remove this assumption so that eventually we can remove this stop_machine() usage altogether. The only reason we'd have to migrate nr_uninterruptible is so that we could use for_each_online_cpu() loops in favour of for_each_possible_cpu() loops, however since nr_uninterruptible() is the only such loop and its using possible lets not bother at all. The problem Rabik sees is (probably) caused by the fact that by migrating nr_uninterruptible we screw rq->calc_load_active for both rqs involved. So don't bother with fancy migration schemes (meaning we now have to keep using for_each_possible_cpu()) and instead fold any nr_active delta after we migrate all tasks away to make sure we don't have any skewed nr_active accounting. [ paulmck: Move call to calc_load_migration to CPU_DEAD to avoid miscounting noted by Rakib. ] Reported-by:
Rakib Mullick <rakib.mullick@gmail.com> Reported-by:
Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:
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Paul E. McKenney authored
Posting a callback after the CPU_DEAD notifier effectively leaks that callback unless/until that CPU comes back online. Silence is unhelpful when attempting to track down such leaks, so this commit emits a WARN_ON_ONCE() and unconditionally leaks the callback when an offline CPU attempts to register a callback. The rdp->nxttail[RCU_NEXT_TAIL] is set to NULL in the CPU_DEAD notifier and restored in the CPU_UP_PREPARE notifier, allowing _call_rcu() to determine exactly when posting callbacks is illegal. Signed-off-by:
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Paul E. McKenney authored
Currently, _rcu_barrier() relies on preempt_disable() to prevent any CPU from going offline, which in turn depends on CPU hotplug's use of __stop_machine(). This patch therefore makes _rcu_barrier() use get_online_cpus() to block CPU-hotplug operations. This has the added benefit of removing the need for _rcu_barrier() to adopt callbacks: Because CPU-hotplug operations are excluded, there can be no callbacks to adopt. This commit simplifies the code accordingly. Signed-off-by:
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Paul E. McKenney authored
The print_cpu_stall_fast_no_hz() function attempts to print -1 when the ->idle_gp_timer is not pending, but unsigned arithmetic causes it to instead print ULONG_MAX, which is 4294967295 on 32-bit systems and 18446744073709551615 on 64-bit systems. Neither of these are the most reader-friendly values, so this commit instead causes "timer not pending" to be printed when ->idle_gp_timer is not pending. Reported-by:
Paul Walmsley <paul@pwsan.com> Signed-off-by:
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Li Zhong authored
TINY_RCU's rcu_idle_enter_common() invokes rcu_sched_qs() in order to inform the RCU core of the quiescent state implied by idle entry. Of course, idle is also an extended quiescent state, so that the call to rcu_sched_qs() speeds up RCU's invoking of any callbacks that might be queued. This speed-up is important when entering into dyntick-idle mode -- if there are no further scheduling-clock interrupts, the callbacks might never be invoked, which could result in a system hang. However, processing callbacks does event tracing, which in turn implies RCU read-side critical sections, which are illegal in extended quiescent states. This patch therefore moves the call to rcu_sched_qs() so that it precedes the point at which we inform lockdep that RCU has entered an extended quiescent state. Signed-off-by:
Li Zhong <zhong@linux.vnet.ibm.com> Signed-off-by:
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Michael Wang authored
This patch replaces list_for_each_continue_rcu() with list_for_each_entry_continue_rcu() to save a few lines of code and allow removing list_for_each_continue_rcu(). Signed-off-by:
Michael Wang <wangyun@linux.vnet.ibm.com> Acked-by:
Catalin Marinas <catalin.marinas@arm.com> Signed-off-by:
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Paul E. McKenney authored
The can_stop_idle_tick() function complains if a softirq vector is raised too late in the idle-entry process, presumably in order to prevent dangling softirq invocations from being delayed across the full idle period, which might be indefinitely long -- and if softirq was asserted any later than the call to this function, such a delay might well happen. However, RCU needs to be able to use softirq to stop idle entry in order to be able to drain RCU callbacks from the current CPU, which in turn enables faster entry into dyntick-idle mode, which in turn reduces power consumption. Because RCU takes this action at a well-defined point in the idle-entry path, it is safe for RCU to take this approach. This commit therefore silences the error message that is sometimes produced when the going-idle CPU suddenly finds that it has an RCU_SOFTIRQ to process. The error message will continue to be issued for other softirq vectors. Reported-by:
Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by:
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Paul E. McKenney authored
The use of raw_local_irq_save() is unnecessary, given that local_irq_save() really does disable interrupts. Also, it appears to interfere with lockdep. Therefore, this commit moves to local_irq_save(). Reported-by:
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Paul E. McKenney authored
The first memory barrier in __call_rcu() is supposed to order any updates done beforehand by the caller against the actual queuing of the callback. However, the second memory barrier (which is intended to order incrementing the queue lengths before queuing the callback) is also between the caller's updates and the queuing of the callback. The second memory barrier can therefore serve both purposes. This commit therefore removes the first memory barrier. Signed-off-by:
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Paul E. McKenney authored
If a given CPU avoids the idle loop but also avoids starting a new RCU grace period for a full minute, RCU can issue spurious RCU CPU stall warnings. This commit fixes this issue by adding a check for ongoing grace period to avoid these spurious stall warnings. Reported-by:
Becky Bruce <bgillbruce@gmail.com> Signed-off-by:
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Paul E. McKenney authored
The print_other_cpu_stall() function accesses a number of rcu_node fields without protection from the ->lock. In theory, this is not a problem because the fields accessed are all integers, but in practice the compiler can get nasty. Therefore, the commit extends the existing critical section to cover the entire loop body. Signed-off-by: -
Paul E. McKenney authored
The rcu_print_detail_task_stall_rnp() function invokes rcu_preempt_blocked_readers_cgp() to verify that there are some preempted RCU readers blocking the current grace period outside of the protection of the rcu_node structure's ->lock. This means that the last blocked reader might exit its RCU read-side critical section and remove itself from the ->blkd_tasks list before the ->lock is acquired, resulting in a segmentation fault when the subsequent code attempts to dereference the now-NULL gp_tasks pointer. This commit therefore moves the test under the lock. This will not have measurable effect on lock contention because this code is invoked only when printing RCU CPU stall warnings, in other words, in the common case, never. Signed-off-by:
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