- 23 Jun, 2017 1 commit
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Thiago Jung Bauermann authored
Calling arch_update_cpu_topology from a CPU hotplug state machine callback hits a deadlock because the function tries to get a read lock on cpu_hotplug_lock while the state machine still holds a write lock on it. Since all callers of arch_update_cpu_topology except rtasd already hold cpu_hotplug_lock, this patch changes the function to use stop_machine_cpuslocked and creates a separate function for rtasd which still tries to obtain the lock. Michael Bringmann investigated the bug and provided a detailed analysis of the deadlock on this previous RFC for an alternate solution: Signed-off-by:
Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Acked-by:
Michael Ellerman <mpe@ellerman.id.au> Cc: John Allen <jallen@linux.vnet.ibm.com> Cc: Michael Bringmann <mwb@linux.vnet.ibm.com> Cc: Nathan Fontenot <nfont@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/1497996510-4032-1-git-send-email-bauerman@linux.vnet.ibm.com Link: https://patchwork.ozlabs.org/patch/771293/
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- 20 Jun, 2017 1 commit
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Tony Lindgren authored
Recent change to use cpuhp_setup_state_cpuslocked() with commit fe2a5cd8 ("ARM/hw_breakpoint: Use cpuhp_setup_state_cpuslocked()") missed to change the related paired cpuhp_remove_state_nocalls_cpuslocked(). Now if arch_hw_breakpoint_init() fails, we get "WARNING: possible recursive locking detected" on the exit path. Fixes: fe2a5cd8 ("ARM/hw_breakpoint: Use cpuhp_setup_state_cpuslocked()") Signed-off-by:
Tony Lindgren <tony@atomide.com> Acked-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Mark Rutland <mark.rutland@arm.com> Cc: linux-omap@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Russell King <linux@armlinux.org.uk> Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/20170616082238.15553-1-tony@atomide.comSigned-off-by:
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- 12 Jun, 2017 1 commit
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Arnd Bergmann authored
clang -Wunused-function found one remaining function that was apparently meant to be removed in a recent code cleanup: kernel/cpu.c:565:20: warning: unused function 'check_for_tasks' [-Wunused-function] Sebastian explained: The function became unused unintentionally, but there is already a failure check, when a task cannot be removed from the outgoing cpu in the scheduler code, so bringing it back is not really giving any extra value. Fixes: 530e9b76 ("cpu/hotplug: Remove obsolete cpu hotplug register/unregister functions") Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Anna-Maria Gleixner <anna-maria@linutronix.de> Link: http://lkml.kernel.org/r/20170608085544.2257132-1-arnd@arndb.deSigned-off-by:
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- 03 Jun, 2017 1 commit
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Alexander Levin authored
If we failed to acquire task's cred_guard_mutex we shouldn't proceed to release it in the error path. Fixes: a63fbed7 ("perf/tracing/cpuhotplug: Fix locking order") Signed-off-by:
Alexander Levin <alexander.levin@verizon.com> Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: mhiramat@kernel.org Cc: paulmck@linux.vnet.ibm.com Cc: bigeasy@linutronix.de Link: http://lkml.kernel.org/r/20170603033903.12056-1-alexander.levin@verizon.comSigned-off-by:
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- 26 May, 2017 32 commits
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Thomas Gleixner authored
The CPU hotplug callbacks are not covered by lockdep versus the cpu hotplug rwsem. CPU0 CPU1 cpuhp_setup_state(STATE, startup, teardown); cpus_read_lock(); invoke_callback_on_ap(); kick_hotplug_thread(ap); wait_for_completion(); hotplug_thread_fn() lock(m); do_stuff(); unlock(m); Lockdep does not know about this dependency and will not trigger on the following code sequence: lock(m); cpus_read_lock(); Add a lockdep map and connect the initiators lock chain with the hotplug thread lock chain, so potential deadlocks can be detected. Signed-off-by:Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by:
Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20170524081549.709375845@linutronix.de
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Thomas Gleixner authored
With the enhanced CPU hotplug lockdep coverage the following lockdep splat happens: ====================================================== WARNING: possible circular locking dependency detected 4.12.0-rc2+ #84 Tainted: G W ------------------------------------------------------ cpuhp/1/15 is trying to acquire lock: flush_work+0x39/0x2f0 but task is already holding lock: cpuhp_thread_fun+0x30/0x160 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (cpuhp_state){+.+.+.}: lock_acquire+0xb4/0x200 cpuhp_kick_ap_work+0x72/0x330 _cpu_down+0x8b/0x100 do_cpu_down+0x3e/0x60 cpu_down+0x10/0x20 cpu_subsys_offline+0x14/0x20 device_offline+0x88/0xb0 online_store+0x4c/0xa0 dev_attr_store+0x18/0x30 sysfs_kf_write+0x45/0x60 kernfs_fop_write+0x156/0x1e0 __vfs_write+0x37/0x160 vfs_write+0xca/0x1c0 SyS_write+0x58/0xc0 entry_SYSCALL_64_fastpath+0x23/0xc2 -> #1 (cpu_hotplug_lock.rw_sem){++++++}: lock_acquire+0xb4/0x200 cpus_read_lock+0x3d/0xb0 apply_workqueue_attrs+0x17/0x50 __alloc_workqueue_key+0x1e1/0x530 scsi_host_alloc+0x373/0x480 [scsi_mod] ata_scsi_add_hosts+0xcb/0x130 [libata] ata_host_register+0x11a/0x2c0 [libata] ata_host_activate+0xf0/0x150 [libata] ahci_host_activate+0x13e/0x170 [libahci] ahci_init_one+0xa3a/0xd3f [ahci] local_pci_probe+0x45/0xa0 work_for_cpu_fn+0x14/0x20 process_one_work+0x1f9/0x690 worker_thread+0x200/0x3d0 kthread+0x138/0x170 ret_from_fork+0x31/0x40 -> #0 ((&wfc.work)){+.+.+.}: __lock_acquire+0x11e1/0x13e0 lock_acquire+0xb4/0x200 flush_work+0x5c/0x2f0 work_on_cpu+0xa1/0xd0 acpi_processor_get_throttling+0x3d/0x50 acpi_processor_reevaluate_tstate+0x2c/0x50 acpi_soft_cpu_online+0x69/0xd0 cpuhp_invoke_callback+0xb4/0x8b0 cpuhp_up_callbacks+0x36/0xc0 cpuhp_thread_fun+0x14e/0x160 smpboot_thread_fn+0x1e8/0x300 kthread+0x138/0x170 ret_from_fork+0x31/0x40 other info that might help us debug this: Chain exists of: (&wfc.work) --> cpu_hotplug_lock.rw_sem --> cpuhp_state Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(cpuhp_state); lock(cpu_hotplug_lock.rw_sem); lock(cpuhp_state); lock((&wfc.work)); *** DEADLOCK *** 1 lock held by cpuhp/1/15: cpuhp_thread_fun+0x30/0x160 stack backtrace: CPU: 1 PID: 15 Comm: cpuhp/1 Tainted: G W 4.12.0-rc2+ #84 Hardware name: Supermicro SYS-4048B-TR4FT/X10QBi, BIOS 1.1a 07/29/2015 Call Trace: dump_stack+0x85/0xc4 print_circular_bug+0x209/0x217 __lock_acquire+0x11e1/0x13e0 lock_acquire+0xb4/0x200 ? lock_acquire+0xb4/0x200 ? flush_work+0x39/0x2f0 ? acpi_processor_start+0x50/0x50 flush_work+0x5c/0x2f0 ? flush_work+0x39/0x2f0 ? acpi_processor_start+0x50/0x50 ? mark_held_locks+0x6d/0x90 ? queue_work_on+0x56/0x90 ? trace_hardirqs_on_caller+0x154/0x1c0 ? trace_hardirqs_on+0xd/0x10 ? acpi_processor_start+0x50/0x50 work_on_cpu+0xa1/0xd0 ? find_worker_executing_work+0x50/0x50 ? acpi_processor_power_exit+0x70/0x70 acpi_processor_get_throttling+0x3d/0x50 acpi_processor_reevaluate_tstate+0x2c/0x50 acpi_soft_cpu_online+0x69/0xd0 cpuhp_invoke_callback+0xb4/0x8b0 ? lock_acquire+0xb4/0x200 ? padata_replace+0x120/0x120 cpuhp_up_callbacks+0x36/0xc0 cpuhp_thread_fun+0x14e/0x160 smpboot_thread_fn+0x1e8/0x300 kthread+0x138/0x170 ? sort_range+0x30/0x30 ? kthread_create_on_node+0x70/0x70 ret_from_fork+0x31/0x40 The problem is that the work is scheduled on the current CPU from the hotplug thread associated with that CPU. It's not required to invoke these functions via the workqueue because the hotplug thread runs on the target CPU already. Check whether current is a per cpu thread pinned on the target CPU and invoke the function directly to avoid the workqueue. Signed-off-by: -
Thomas Gleixner authored
Provide a helper function for checking whether current task is a per cpu thread. Signed-off-by:
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Thomas Gleixner authored
There are no more (known) nested calls to get_online_cpus() and all observed lock ordering problems have been addressed. Replace the magic nested 'rwsem' hackery with a percpu-rwsem. Signed-off-by:
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Thomas Gleixner authored
The text patching functions which are invoked from jump_label and kprobes code are protected against cpu hotplug at the call sites. Use stop_machine_cpuslocked() to avoid recursion on the cpu hotplug rwsem. stop_machine_cpuslocked() contains a lockdep assertion to catch any unprotected callers. Signed-off-by:
Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: linux-s390@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Link: http://lkml.kernel.org/r/20170524081549.354513406@linutronix.de
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Thomas Gleixner authored
The text patching functions which are invoked from jump_label and kprobes code are protected against cpu hotplug at the call sites. Use stop_machine_cpuslocked() to avoid recursion on the cpu hotplug rwsem. stop_machine_cpuslocked() contains a lockdep assertion to catch any unprotected callers. Signed-off-by:
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Thomas Gleixner authored
The text patching functions which are invoked from jump_label and kprobes code are protected against cpu hotplug at the call sites. Use stop_machine_cpuslocked() to avoid recursion on the cpu hotplug rwsem. stop_machine_cpuslocked() contains a lockdep assertion to catch any unprotected callers. Signed-off-by:
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Thomas Gleixner authored
Converting the cpu hotplug locking to a percpu rwsem unearthed hidden lock ordering problems. There is a wide range of locks involved in this: kprobe_mutex, jump_label_mutex, ftrace_lock, text_mutex, event_mutex, module_mutex, func_hash->regex_lock and a gazillion of lock order permutations with nested get_online_cpus() calls. Some of those permutations are potential deadlocks even with the current nesting hotplug locking scheme, but they can't be discovered by lockdep. The conversion of the hotplug locking to a percpu rwsem requires to prevent nested locking, so it's required to take the hotplug rwsem early in the call chain and establish a proper lock order. After quite some analysis and going down the wrong road severa times the following lock order has been chosen: kprobe_mutex -> cpus_rwsem -> jump_label_mutex -> text_mutex For kprobes which hook on an ftrace function trace point, it's required to drop cpus_rwsem before calling into the ftrace code to avoid a deadlock on the func_hash->regex_lock. [ Steven: Ftrace interaction fixes ] Signed-off-by:
Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
Masami Hiramatsu <mhiramat@kernel.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Link: http://lkml.kernel.org/r/20170524081549.104864779@linutronix.de
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Thomas Gleixner authored
The conversion of the hotplug locking to a percpu rwsem unearthed lock ordering issues all over the place. The jump_label code has two issues: 1) Nested get_online_cpus() invocations 2) Ordering problems vs. the cpus rwsem and the jump_label_mutex To cure these, the following lock order has been established; cpus_rwsem -> jump_label_lock -> text_mutex Even if not all architectures need protection against CPU hotplug, taking cpus_rwsem before jump_label_lock is now mandatory in code pathes which actually modify code and therefor need text_mutex protection. Move the get_online_cpus() invocations into the core jump label code and establish the proper lock order where required. Signed-off-by:
"David S. Miller" <davem@davemloft.net> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Ralf Baechle <ralf@linux-mips.org> Link: http://lkml.kernel.org/r/20170524081549.025830817@linutronix.de
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Thomas Gleixner authored
perf, tracing, kprobes and jump_labels have a gazillion of ways to create dependency lock chains. Some of those involve nested invocations of get_online_cpus(). The conversion of the hotplug locking to a percpu rwsem requires to avoid such nested calls. sys_perf_event_open() protects most of the syscall logic against cpu hotplug. This causes nested calls and lock inversions versus ftrace and kprobes in various interesting ways. It's impossible to move the hotplug locking to the outer end of all call chains in the involved facilities, so the hotplug protection in sys_perf_event_open() needs to be solved differently. Introduce 'pmus_mutex' which protects a perf private online cpumask. This mutex is taken when the mask is updated in the cpu hotplug callbacks and can be taken in sys_perf_event_open() to protect the swhash setup/teardown code and when the final judgement about a valid event has to be made. [ tglx: Produced changelog and fixed the swhash interaction ] Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by:
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Thomas Gleixner authored
Converting the hotplug locking, i.e. get_online_cpus(), to a percpu rwsem unearthed a circular lock dependency which was hidden from lockdep due to the lockdep annotation of get_online_cpus() which prevents lockdep from creating full dependency chains. CPU0 CPU1 ---- ---- lock((&wfc.work)); lock(cpu_hotplug_lock.rw_sem); lock((&wfc.work)); lock(cpu_hotplug_lock.rw_sem); This dependency is established via acpi_processor_start() which calls into the work queue code. And the work queue code establishes the reverse dependency. This is not a problem of get_online_cpus() recursion, it's a possible deadlock undetected by lockdep so far. The cure is to use cpu_hotplug_disable() instead of get_online_cpus() to protect the probing from acpi_processor_start(). There is a side effect to this: cpu_hotplug_disable() makes a concurrent cpu hotplug attempt via the sysfs interfaces fail with -EBUSY, but that probing usually happens during the boot process where no interaction is possible. Any later invocations are infrequent enough and concurrent hotplug attempts are so unlikely that the danger of user space visible regressions is very close to zero. Anyway, thats preferrable over a real deadlock. Signed-off-by:Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: linux-acpi@vger.kernel.org Cc: Len Brown <lenb@kernel.org> Link: http://lkml.kernel.org/r/20170524081548.851588594@linutronix.de
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Thomas Gleixner authored
pci_call_probe() can called recursively when a physcial function is probed and the probing creates virtual functions, which are populated via pci_bus_add_device() which in turn can end up calling pci_call_probe() again. The code has an interesting way to prevent recursing into the workqueue code. That's accomplished by a check whether the current task runs already on the numa node which is associated with the device. While that works to prevent the recursion into the workqueue code, it's racy versus normal execution as there is no guarantee that the node does not vanish after the check. There is another issue with this code. It dereferences cpumask_of_node() unconditionally without checking whether the node is available. Make the detection reliable by: - Mark a probed device as 'is_probed' in pci_call_probe() - Check in pci_call_probe for a virtual function. If it's a virtual function and the associated physical function device is marked 'is_probed' then this is a recursive call, so the call can be invoked in the calling context. - Add a check whether the node is online before dereferencing it. Signed-off-by:
Bjorn Helgaas <bhelgaas@google.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: linux-pci@vger.kernel.org Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20170524081548.771457199@linutronix.de
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Thomas Gleixner authored
Converting the hotplug locking, i.e. get_online_cpus(), to a percpu rwsem unearthed a circular lock dependency which was hidden from lockdep due to the lockdep annotation of get_online_cpus() which prevents lockdep from creating full dependency chains. There are several variants of this. And example is: Chain exists of: cpu_hotplug_lock.rw_sem --> drm_global_mutex --> &item->mutex CPU0 CPU1 ---- ---- lock(&item->mutex); lock(drm_global_mutex); lock(&item->mutex); lock(cpu_hotplug_lock.rw_sem); because there are dependencies through workqueues. The call chain is: get_online_cpus apply_workqueue_attrs __alloc_workqueue_key ttm_mem_global_init ast_ttm_mem_global_init drm_global_item_ref ast_mm_init ast_driver_load drm_dev_register drm_get_pci_dev ast_pci_probe local_pci_probe work_for_cpu_fn process_one_work worker_thread This is not a problem of get_online_cpus() recursion, it's a possible deadlock undetected by lockdep so far. The cure is to use cpu_hotplug_disable() instead of get_online_cpus() to protect the PCI probing. There is a side effect to this: cpu_hotplug_disable() makes a concurrent cpu hotplug attempt via the sysfs interfaces fail with -EBUSY, but PCI probing usually happens during the boot process where no interaction is possible. Any later invocations are infrequent enough and concurrent hotplug attempts are so unlikely that the danger of user space visible regressions is very close to zero. Anyway, thats preferrable over a real deadlock. Signed-off-by: -
Sebastian Andrzej Siewior authored
If intel_snb_check_microcode() is invoked via microcode_init -> perf_check_microcode -> intel_snb_check_microcode then get_online_cpus() is invoked nested. This works with the current implementation of get_online_cpus() but prevents converting it to a percpu rwsem. intel_snb_check_microcode() is also invoked from intel_sandybridge_quirk() unprotected. Drop get_online_cpus() from intel_snb_check_microcode() and add it to intel_sandybridge_quirk() so both call sites are protected. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
Borislav Petkov <bp@suse.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Borislav Petkov <bp@alien8.de> Link: http://lkml.kernel.org/r/20170524081548.594862191@linutronix.de
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Thomas Gleixner authored
The only caller is the microcode update, which cannot be modular. Drop the export. Signed-off-by:
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Sebastian Andrzej Siewior authored
takedown_cpu() is a cpu hotplug function invoking stop_machine(). The cpu hotplug machinery holds the hotplug lock for write. stop_machine() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use stop_machine_cpuslocked() to avoid the nested call. Signed-off-by:
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Sebastian Andrzej Siewior authored
set_subcores_per_core() holds get_online_cpus() while invoking stop_machine(). stop_machine() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use stop_machine_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
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Sebastian Andrzej Siewior authored
stp_work_fn() holds get_online_cpus() while invoking stop_machine(). stop_machine() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use stop_machine_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
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Sebastian Andrzej Siewior authored
arch_hw_breakpoint_init() holds get_online_cpus() while registerring the hotplug callbacks. cpuhp_setup_state() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use cpuhp_setup_state_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
Mark Rutland <mark.rutland@arm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Russell King <linux@armlinux.org.uk> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/20170524081548.170940729@linutronix.de
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Sebastian Andrzej Siewior authored
intel_cqm_init() holds get_online_cpus() while registerring the hotplug callbacks. cpuhp_setup_state() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use cpuhp_setup_state_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
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Sebastian Andrzej Siewior authored
etm_probe4() holds get_online_cpus() while invoking cpuhp_setup_state_nocalls(). cpuhp_setup_state_nocalls() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use cpuhp_setup_state_nocalls_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/20170524081547.983493849@linutronix.de
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Sebastian Andrzej Siewior authored
etm_probe() holds get_online_cpus() while invoking cpuhp_setup_state_nocalls(). cpuhp_setup_state_nocalls() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use cpuhp_setup_state_nocalls_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
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Sebastian Andrzej Siewior authored
kvmppc_alloc_host_rm_ops() holds get_online_cpus() while invoking cpuhp_setup_state_nocalls(). cpuhp_setup_state_nocalls() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use cpuhp_setup_state_nocalls_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
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Sebastian Andrzej Siewior authored
cpufreq holds get_online_cpus() while invoking cpuhp_setup_state_nocalls() to make subsys_interface_register() and the registration of hotplug calls atomic versus cpu hotplug. cpuhp_setup_state_nocalls() invokes get_online_cpus() as well. This is correct, but prevents the conversion of the hotplug locking to a percpu rwsem. Use cpuhp_setup/remove_state_nocalls_cpuslocked() to avoid the nested call. Convert *_online_cpus() to the new interfaces while at it. Signed-off-by:
Viresh Kumar <viresh.kumar@linaro.org> Cc: linux-pm@vger.kernel.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20170524081547.731628408@linutronix.de
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Sebastian Andrzej Siewior authored
mtrr_save_state() is invoked from native_cpu_up() which is in the context of a CPU hotplug operation and therefor calling get_online_cpus() is pointless. While this works in the current get_online_cpus() implementation it prevents from converting the hotplug locking to percpu rwsems. Remove it. Signed-off-by:
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Sebastian Andrzej Siewior authored
pcrypt_init_padata() cpus_read_lock() padata_alloc_possible() padata_alloc() cpus_read_lock() The nested call to cpus_read_lock() works with the current implementation, but prevents the conversion to a percpu rwsem. The other caller of padata_alloc_possible() is pcrypt_init_padata() which calls from a cpus_read_lock() protected region as well. Remove the cpus_read_lock() call in padata_alloc() and document the calling convention. Signed-off-by: -
Thomas Gleixner authored
No users outside of padata.c Signed-off-by:
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Sebastian Andrzej Siewior authored
Some call sites of stop_machine() are within a get_online_cpus() protected region. stop_machine() calls get_online_cpus() as well, which is possible in the current implementation but prevents converting the hotplug locking to a percpu rwsem. Provide stop_machine_cpuslocked() to avoid nested calls to get_online_cpus(). Signed-off-by:
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Thomas Gleixner authored
Add cpuslocked() variants for the multi instance registration so this can be called from a cpus_read_lock() protected region. Signed-off-by:
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Sebastian Andrzej Siewior authored
Some call sites of cpuhp_setup/remove_state[_nocalls]() are within a cpus_read locked region. cpuhp_setup/remove_state[_nocalls]() call cpus_read_lock() as well, which is possible in the current implementation but prevents converting the hotplug locking to a percpu rwsem. Provide locked versions of the interfaces to avoid nested calls to cpus_read_lock(). Signed-off-by:
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Thomas Gleixner authored
Provide a stub function which can be used in places where existing get_online_cpus() calls are moved to call sites. This stub is going to be filled by the final conversion of the hotplug locking mechanism to a percpu rwsem. Signed-off-by:
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Thomas Gleixner authored
The counting 'rwsem' hackery of get|put_online_cpus() is going to be replaced by percpu rwsem. Rename the functions to make it clear that it's locking and not some refcount style interface. These new functions will be used for the preparatory patches which make the code ready for the percpu rwsem conversion. Rename all instances in the cpu hotplug code while at it. Signed-off-by:
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- 22 May, 2017 2 commits
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Linus Torvalds authored
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Linus Torvalds authored
The code to fetch a 64-bit value from user space was entirely buggered, and has been since the code was merged in early 2016 in commit b2f68038 ("x86/mm/32: Add support for 64-bit __get_user() on 32-bit kernels"). Happily the buggered routine is almost certainly entirely unused, since the normal way to access user space memory is just with the non-inlined "get_user()", and the inlined version didn't even historically exist. The normal "get_user()" case is handled by external hand-written asm in arch/x86/lib/getuser.S that doesn't have either of these issues. There were two independent bugs in __get_user_asm_u64(): - it still did the STAC/CLAC user space access marking, even though that is now done by the wrapper macros, see commit 11f1a4b9 ("x86: reorganize SMAP handling in user space accesses"). This didn't result in a semantic error, it just means that the inlined optimized version was hugely less efficient than the allegedly slower standard version, since the CLAC/STAC overhead is quite high on modern Intel CPU's. - the double register %eax/%edx was marked as an output, but the %eax part of it was touched early in the asm, and could thus clobber other inputs to the asm that gcc didn't expect it to touch. In particular, that meant that the generated code could look like this: mov (%eax),%eax mov 0x4(%eax),%edx where the load of %edx obviously was _supposed_ to be from the 32-bit word that followed the source of %eax, but because %eax was overwritten by the first instruction, the source of %edx was basically random garbage. The fixes are trivial: remove the extraneous STAC/CLAC entries, and mark the 64-bit output as early-clobber to let gcc know that no inputs should alias with the output register. Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: stable@kernel.org # v4.8+ Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- 21 May, 2017 2 commits
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Linus Torvalds authored
Al noticed that unsafe_put_user() had type problems, and fixed them in commit a7cc722f ("fix unsafe_put_user()"), which made me look more at those functions. It turns out that unsafe_get_user() had a type issue too: it limited the largest size of the type it could handle to "unsigned long". Which is fine with the current users, but doesn't match our existing normal get_user() semantics, which can also handle "u64" even when that does not fit in a long. While at it, also clean up the type cast in unsafe_put_user(). We actually want to just make it an assignment to the expected type of the pointer, because we actually do want warnings from types that don't convert silently. And it makes the code more readable by not having that one very long and complex line. [ This patch might become stable material if we ever end up back-porting any new users of the unsafe uaccess code, but as things stand now this doesn't matter for any current existing uses. ] Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by:
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfsLinus Torvalds authored
Pull misc uaccess fixes from Al Viro: "Fix for unsafe_put_user() (no callers currently in mainline, but anyone starting to use it will step into that) + alpha osf_wait4() infoleak fix" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: osf_wait4(): fix infoleak fix unsafe_put_user()
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