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2020-03-25cpu/hotplug: Add new {add,remove}_cpu() functionsQais Yousef
The new functions use device_{online,offline}() which are userspace safe. This is in preparation to move cpu_{up, down} kernel users to use a safer interface that is not racy with userspace. Suggested-by: "Paul E. McKenney" <paulmck@kernel.org> Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lkml.kernel.org/r/20200323135110.30522-2-qais.yousef@arm.com
2020-03-25.gitignore: add SPDX License IdentifierMasahiro Yamada
Add SPDX License Identifier to all .gitignore files. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-25.gitignore: remove too obvious commentsMasahiro Yamada
Some .gitignore files have comments like "Generated files", "Ignore generated files" at the header part, but they are too obvious. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-24Merge branch 'for-mingo' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu Pull RCU changes from Paul E. McKenney: - Make kfree_rcu() use kfree_bulk() for added performance - RCU updates - Callback-overload handling updates - Tasks-RCU KCSAN and sparse updates - Locking torture test and RCU torture test updates - Documentation updates - Miscellaneous fixes Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-23completion: Use lockdep_assert_RT_in_threaded_ctx() in complete_all()Sebastian Siewior
The warning was intended to spot complete_all() users from hardirq context on PREEMPT_RT. The warning as-is will also trigger in interrupt handlers, which are threaded on PREEMPT_RT, which was not intended. Use lockdep_assert_RT_in_threaded_ctx() which triggers in non-preemptive context on PREEMPT_RT. Fixes: a5c6234e1028 ("completion: Use simple wait queues") Reported-by: kernel test robot <rong.a.chen@intel.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200323152019.4qjwluldohuh3by5@linutronix.de
2020-03-23fsnotify: use helpers to access data by data_typeAmir Goldstein
Create helpers to access path and inode from different data types. Link: https://lore.kernel.org/r/20200319151022.31456-5-amir73il@gmail.com Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
2020-03-23PM: remove s390 specific callbacksHeiko Carstens
ARCH_SAVE_PAGE_KEYS has been introduced in order to be able to save and restore s390 specific storage keys into a hibernation image. With hibernation support removed from s390 there is no point in keeping the callbacks. Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2020-03-23Merge 5.6-rc7 into tty-nextGreg Kroah-Hartman
We need the tty fixes in here as well. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-23Merge 5.6-rc7 into char-misc-nextGreg Kroah-Hartman
We need the char/misc driver fixes in here as well. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-21x86/mm: split vmalloc_sync_all()Joerg Roedel
Commit 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") introduced a call to vmalloc_sync_all() in the vunmap() code-path. While this change was necessary to maintain correctness on x86-32-pae kernels, it also adds additional cycles for architectures that don't need it. Specifically on x86-64 with CONFIG_VMAP_STACK=y some people reported severe performance regressions in micro-benchmarks because it now also calls the x86-64 implementation of vmalloc_sync_all() on vunmap(). But the vmalloc_sync_all() implementation on x86-64 is only needed for newly created mappings. To avoid the unnecessary work on x86-64 and to gain the performance back, split up vmalloc_sync_all() into two functions: * vmalloc_sync_mappings(), and * vmalloc_sync_unmappings() Most call-sites to vmalloc_sync_all() only care about new mappings being synchronized. The only exception is the new call-site added in the above mentioned commit. Shile Zhang directed us to a report of an 80% regression in reaim throughput. Fixes: 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") Reported-by: kernel test robot <oliver.sang@intel.com> Reported-by: Shile Zhang <shile.zhang@linux.alibaba.com> Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Borislav Petkov <bp@suse.de> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> [GHES] Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20191009124418.8286-1-joro@8bytes.org Link: https://lists.01.org/hyperkitty/list/lkp@lists.01.org/thread/4D3JPPHBNOSPFK2KEPC6KGKS6J25AIDB/ Link: http://lkml.kernel.org/r/20191113095530.228959-1-shile.zhang@linux.alibaba.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-03-21Merge branches 'doc.2020.02.27a', 'fixes.2020.03.21a', ↵Paul E. McKenney
'kfree_rcu.2020.02.20a', 'locktorture.2020.02.20a', 'ovld.2020.02.20a', 'rcu-tasks.2020.02.20a', 'srcu.2020.02.20a' and 'torture.2020.02.20a' into HEAD doc.2020.02.27a: Documentation updates. fixes.2020.03.21a: Miscellaneous fixes. kfree_rcu.2020.02.20a: Updates to kfree_rcu(). locktorture.2020.02.20a: Lock torture-test updates. ovld.2020.02.20a: Updates to callback-overload handling. rcu-tasks.2020.02.20a: RCU-tasks updates. srcu.2020.02.20a: SRCU updates. torture.2020.02.20a: Torture-test updates.
2020-03-21rcu: Make rcu_barrier() account for offline no-CBs CPUsPaul E. McKenney
Currently, rcu_barrier() ignores offline CPUs, However, it is possible for an offline no-CBs CPU to have callbacks queued, and rcu_barrier() must wait for those callbacks. This commit therefore makes rcu_barrier() directly invoke the rcu_barrier_func() with interrupts disabled for such CPUs. This requires passing the CPU number into this function so that it can entrain the rcu_barrier() callback onto the correct CPU's callback list, given that the code must instead execute on the current CPU. While in the area, this commit fixes a bug where the first CPU's callback might have been invoked before rcu_segcblist_entrain() returned, which would also result in an early wakeup. Fixes: 5d6742b37727 ("rcu/nocb: Use rcu_segcblist for no-CBs CPUs") Signed-off-by: Paul E. McKenney <paulmck@kernel.org> [ paulmck: Apply optimization feedback from Boqun Feng. ] Cc: <stable@vger.kernel.org> # 5.5.x
2020-03-21rcu: Mark rcu_state.gp_seq to detect concurrent writesPaul E. McKenney
The rcu_state structure's gp_seq field is only to be modified by the RCU grace-period kthread, which is single-threaded. This commit therefore enlists KCSAN's help in enforcing this restriction. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-03-21genirq: Fix reference leaks on irq affinity notifiersEdward Cree
The handling of notify->work did not properly maintain notify->kref in two cases: 1) where the work was already scheduled, another irq_set_affinity_locked() would get the ref and (no-op-ly) schedule the work. Thus when irq_affinity_notify() ran, it would drop the original ref but not the additional one. 2) when cancelling the (old) work in irq_set_affinity_notifier(), if there was outstanding work a ref had been got for it but was never put. Fix both by checking the return values of the work handling functions (schedule_work() for (1) and cancel_work_sync() for (2)) and put the extra ref if the return value indicates preexisting work. Fixes: cd7eab44e994 ("genirq: Add IRQ affinity notifiers") Fixes: 59c39840f5ab ("genirq: Prevent use-after-free and work list corruption") Signed-off-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ben Hutchings <ben@decadent.org.uk> Link: https://lkml.kernel.org/r/24f5983f-2ab5-e83a-44ee-a45b5f9300f5@solarflare.com
2020-03-21lockdep: Rename trace_{hard,soft}{irq_context,irqs_enabled}()Peter Zijlstra
Continue what commit: d820ac4c2fa8 ("locking: rename trace_softirq_[enter|exit] => lockdep_softirq_[enter|exit]") started, rename these to avoid confusing them with tracepoints. git grep -l "trace_\(soft\|hard\)\(irq_context\|irqs_enabled\)" | while read file; do sed -ie 's/trace_\(soft\|hard\)\(irq_context\|irqs_enabled\)/lockdep_\1\2/g' $file; done Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Will Deacon <will@kernel.org> Link: https://lkml.kernel.org/r/20200320115859.178626842@infradead.org
2020-03-21lockdep: Rename trace_softirqs_{on,off}()Peter Zijlstra
Continue what commit: d820ac4c2fa8 ("locking: rename trace_softirq_[enter|exit] => lockdep_softirq_[enter|exit]") started, rename these to avoid confusing them with tracepoints. git grep -l "trace_softirqs_\(on\|off\)" | while read file; do sed -ie 's/trace_softirqs_\(on\|off\)/lockdep_softirqs_\1/g' $file; done Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Will Deacon <will@kernel.org> Link: https://lkml.kernel.org/r/20200320115859.119434738@infradead.org
2020-03-21lockdep: Rename trace_hardirq_{enter,exit}()Thomas Gleixner
Continue what commit: d820ac4c2fa8 ("locking: rename trace_softirq_[enter|exit] => lockdep_softirq_[enter|exit]") started, rename these to avoid confusing them with tracepoints. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Will Deacon <will@kernel.org> Link: https://lkml.kernel.org/r/20200320115859.060481361@infradead.org
2020-03-21lockdep: Add posixtimer context tracing bitsSebastian Andrzej Siewior
Splitting run_posix_cpu_timers() into two parts is work in progress which is stuck on other entry code related problems. The heavy lifting which involves locking of sighand lock will be moved into task context so the necessary execution time is burdened on the task and not on interrupt context. Until this work completes lockdep with the spinlock nesting rules enabled would emit warnings for this known context. Prevent it by setting "->irq_config = 1" for the invocation of run_posix_cpu_timers() so lockdep does not complain when sighand lock is acquried. This will be removed once the split is completed. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.751182723@linutronix.de
2020-03-21lockdep: Annotate irq_workSebastian Andrzej Siewior
Mark irq_work items with IRQ_WORK_HARD_IRQ which should be invoked in hardirq context even on PREEMPT_RT. IRQ_WORK without this flag will be invoked in softirq context on PREEMPT_RT. Set ->irq_config to 1 for the IRQ_WORK items which are invoked in softirq context so lockdep knows that these can safely acquire a spinlock_t. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.643576700@linutronix.de
2020-03-21lockdep: Add hrtimer context tracing bitsSebastian Andrzej Siewior
Set current->irq_config = 1 for hrtimers which are not marked to expire in hard interrupt context during hrtimer_init(). These timers will expire in softirq context on PREEMPT_RT. Setting this allows lockdep to differentiate these timers. If a timer is marked to expire in hard interrupt context then the timer callback is not supposed to acquire a regular spinlock instead of a raw_spinlock in the expiry callback. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.534508206@linutronix.de
2020-03-21lockdep: Introduce wait-type checksPeter Zijlstra
Extend lockdep to validate lock wait-type context. The current wait-types are: LD_WAIT_FREE, /* wait free, rcu etc.. */ LD_WAIT_SPIN, /* spin loops, raw_spinlock_t etc.. */ LD_WAIT_CONFIG, /* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */ LD_WAIT_SLEEP, /* sleeping locks, mutex_t etc.. */ Where lockdep validates that the current lock (the one being acquired) fits in the current wait-context (as generated by the held stack). This ensures that there is no attempt to acquire mutexes while holding spinlocks, to acquire spinlocks while holding raw_spinlocks and so on. In other words, its a more fancy might_sleep(). Obviously RCU made the entire ordeal more complex than a simple single value test because RCU can be acquired in (pretty much) any context and while it presents a context to nested locks it is not the same as it got acquired in. Therefore its necessary to split the wait_type into two values, one representing the acquire (outer) and one representing the nested context (inner). For most 'normal' locks these two are the same. [ To make static initialization easier we have the rule that: .outer == INV means .outer == .inner; because INV == 0. ] It further means that its required to find the minimal .inner of the held stack to compare against the outer of the new lock; because while 'normal' RCU presents a CONFIG type to nested locks, if it is taken while already holding a SPIN type it obviously doesn't relax the rules. Below is an example output generated by the trivial test code: raw_spin_lock(&foo); spin_lock(&bar); spin_unlock(&bar); raw_spin_unlock(&foo); [ BUG: Invalid wait context ] ----------------------------- swapper/0/1 is trying to lock: ffffc90000013f20 (&bar){....}-{3:3}, at: kernel_init+0xdb/0x187 other info that might help us debug this: 1 lock held by swapper/0/1: #0: ffffc90000013ee0 (&foo){+.+.}-{2:2}, at: kernel_init+0xd1/0x187 The way to read it is to look at the new -{n,m} part in the lock description; -{3:3} for the attempted lock, and try and match that up to the held locks, which in this case is the one: -{2,2}. This tells that the acquiring lock requires a more relaxed environment than presented by the lock stack. Currently only the normal locks and RCU are converted, the rest of the lockdep users defaults to .inner = INV which is ignored. More conversions can be done when desired. The check for spinlock_t nesting is not enabled by default. It's a separate config option for now as there are known problems which are currently addressed. The config option allows to identify these problems and to verify that the solutions found are indeed solving them. The config switch will be removed and the checks will permanently enabled once the vast majority of issues has been addressed. [ bigeasy: Move LD_WAIT_FREE,… out of CONFIG_LOCKDEP to avoid compile failure with CONFIG_DEBUG_SPINLOCK + !CONFIG_LOCKDEP] [ tglx: Add the config option ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.427089655@linutronix.de
2020-03-21completion: Use simple wait queuesThomas Gleixner
completion uses a wait_queue_head_t to enqueue waiters. wait_queue_head_t contains a spinlock_t to protect the list of waiters which excludes it from being used in truly atomic context on a PREEMPT_RT enabled kernel. The spinlock in the wait queue head cannot be replaced by a raw_spinlock because: - wait queues can have custom wakeup callbacks, which acquire other spinlock_t locks and have potentially long execution times - wake_up() walks an unbounded number of list entries during the wake up and may wake an unbounded number of waiters. For simplicity and performance reasons complete() should be usable on PREEMPT_RT enabled kernels. completions do not use custom wakeup callbacks and are usually single waiter, except for a few corner cases. Replace the wait queue in the completion with a simple wait queue (swait), which uses a raw_spinlock_t for protecting the waiter list and therefore is safe to use inside truly atomic regions on PREEMPT_RT. There is no semantical or functional change: - completions use the exclusive wait mode which is what swait provides - complete() wakes one exclusive waiter - complete_all() wakes all waiters while holding the lock which protects the wait queue against newly incoming waiters. The conversion to swait preserves this behaviour. complete_all() might cause unbound latencies with a large number of waiters being woken at once, but most complete_all() usage sites are either in testing or initialization code or have only a really small number of concurrent waiters which for now does not cause a latency problem. Keep it simple for now. The fixup of the warning check in the USB gadget driver is just a straight forward conversion of the lockless waiter check from one waitqueue type to the other. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lkml.kernel.org/r/20200321113242.317954042@linutronix.de
2020-03-21sched/swait: Prepare usage in completionsThomas Gleixner
As a preparation to use simple wait queues for completions: - Provide swake_up_all_locked() to support complete_all() - Make __prepare_to_swait() public available This is done to enable the usage of complete() within truly atomic contexts on a PREEMPT_RT enabled kernel. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.228481202@linutronix.de
2020-03-21timekeeping: Split jiffies seqlockThomas Gleixner
seqlock consists of a sequence counter and a spinlock_t which is used to serialize the writers. spinlock_t is substituted by a "sleeping" spinlock on PREEMPT_RT enabled kernels which breaks the usage in the timekeeping code as the writers are executed in hard interrupt and therefore non-preemptible context even on PREEMPT_RT. The spinlock in seqlock cannot be unconditionally replaced by a raw_spinlock_t as many seqlock users have nesting spinlock sections or other code which is not suitable to run in truly atomic context on RT. Instead of providing a raw_seqlock API for a single use case, open code the seqlock for the jiffies use case and implement it with a raw_spinlock_t and a sequence counter. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.120587764@linutronix.de
2020-03-21rcuwait: Add @state argument to rcuwait_wait_event()Peter Zijlstra (Intel)
Extend rcuwait_wait_event() with a state variable so that it is not restricted to UNINTERRUPTIBLE waits. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113241.824030968@linutronix.de
2020-03-21kcsan, trace: Make KCSAN compatible with tracingMarco Elver
Previously the system would lock up if ftrace was enabled together with KCSAN. This is due to recursion on reporting if the tracer code is instrumented with KCSAN. To avoid this for all types of tracing, disable KCSAN instrumentation for all of kernel/trace. Furthermore, since KCSAN relies on udelay() to introduce delay, we have to disable ftrace for udelay() (currently done for x86) in case KCSAN is used together with lockdep and ftrace. The reason is that it may corrupt lockdep IRQ flags tracing state due to a peculiar case of recursion (details in Makefile comment). Reported-by: Qian Cai <cai@lca.pw> Tested-by: Qian Cai <cai@lca.pw> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Introduce ASSERT_EXCLUSIVE_BITS(var, mask)Marco Elver
This introduces ASSERT_EXCLUSIVE_BITS(var, mask). ASSERT_EXCLUSIVE_BITS(var, mask) will cause KCSAN to assume that the following access is safe w.r.t. data races (however, please see the docbook comment for disclaimer here). For more context on why this was considered necessary, please see: http://lkml.kernel.org/r/1580995070-25139-1-git-send-email-cai@lca.pw In particular, before this patch, data races between reads (that use @mask bits of an access that should not be modified concurrently) and writes (that change ~@mask bits not used by the readers) would have been annotated with "data_race()" (or "READ_ONCE()"). However, doing so would then hide real problems: we would no longer be able to detect harmful races between reads to @mask bits and writes to @mask bits. Therefore, by using ASSERT_EXCLUSIVE_BITS(var, mask), we accomplish: 1. Avoid proliferation of specific macros at the call sites: by including a single mask in the argument list, we can use the same macro in a wide variety of call sites, regardless of how and which bits in a field each call site actually accesses. 2. The existing code does not need to be modified (although READ_ONCE() may still be advisable if we cannot prove that the data race is always safe). 3. We catch bugs where the exclusive bits are modified concurrently. 4. We document properties of the current code. Acked-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: David Hildenbrand <david@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Qian Cai <cai@lca.pw>
2020-03-21kcsan: Add kcsan_set_access_mask() supportMarco Elver
When setting up an access mask with kcsan_set_access_mask(), KCSAN will only report races if concurrent changes to bits set in access_mask are observed. Conveying access_mask via a separate call avoids introducing overhead in the common-case fast-path. Acked-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Introduce kcsan_value_change typeMarco Elver
Introduces kcsan_value_change type, which explicitly points out if we either observed a value-change (TRUE), or we could not observe one but cannot rule out a value-change happened (MAYBE). The MAYBE state can either be reported or not, depending on configuration preferences. A follow-up patch introduces the FALSE state, which should never be reported. No functional change intended. Acked-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Fix misreporting if concurrent races on same addressMarco Elver
If there are at least 4 threads racing on the same address, it can happen that one of the readers may observe another matching reader in other_info. To avoid locking up, we have to consume 'other_info' regardless, but skip the report. See the added comment for more details. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Expose core configuration parameters as module paramsMarco Elver
This adds early_boot, udelay_{task,interrupt}, and skip_watch as module params. The latter parameters are useful to modify at runtime to tune KCSAN's performance on new systems. This will also permit auto-tuning these parameters to maximize overall system performance and KCSAN's race detection ability. None of the parameters are used in the fast-path and referring to them via static variables instead of CONFIG constants will not affect performance. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Qian Cai <cai@lca.pw>
2020-03-21kcsan: Add test to generate conflicts via debugfsMarco Elver
Add 'test=<iters>' option to KCSAN's debugfs interface to invoke KCSAN checks on a dummy variable. By writing 'test=<iters>' to the debugfs file from multiple tasks, we can generate real conflicts, and trigger data race reports. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Introduce KCSAN_ACCESS_ASSERT access typeMarco Elver
The KCSAN_ACCESS_ASSERT access type may be used to introduce dummy reads and writes to assert certain properties of concurrent code, where bugs could not be detected as normal data races. For example, a variable that is only meant to be written by a single CPU, but may be read (without locking) by other CPUs must still be marked properly to avoid data races. However, concurrent writes, regardless if WRITE_ONCE() or not, would be a bug. Using kcsan_check_access(&x, sizeof(x), KCSAN_ACCESS_ASSERT) would allow catching such bugs. To support KCSAN_ACCESS_ASSERT the following notable changes were made: * If an access is of type KCSAN_ASSERT_ACCESS, disable various filters that only apply to data races, so that all races that KCSAN observes are reported. * Bug reports that involve an ASSERT access type will be reported as "KCSAN: assert: race in ..." instead of "data-race"; this will help more easily distinguish them. * Update a few comments to just mention 'races' where we do not always mean pure data races. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Fix 0-sized checksMarco Elver
Instrumentation of arbitrary memory-copy functions, such as user-copies, may be called with size of 0, which could lead to false positives. To avoid this, add a comparison in check_access() for size==0, which will be optimized out for constant sized instrumentation (__tsan_{read,write}N), and therefore not affect the common-case fast-path. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Add option to assume plain aligned writes up to word size are atomicMarco Elver
This adds option KCSAN_ASSUME_PLAIN_WRITES_ATOMIC. If enabled, plain aligned writes up to word size are assumed to be atomic, and also not subject to other unsafe compiler optimizations resulting in data races. This option has been enabled by default to reflect current kernel-wide preferences. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Address missing case with KCSAN_REPORT_VALUE_CHANGE_ONLYMarco Elver
Even with KCSAN_REPORT_VALUE_CHANGE_ONLY, KCSAN still reports data races between reads and watchpointed writes, even if the writes wrote values already present. This commit causes KCSAN to unconditionally skip reporting in this case. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Make KCSAN compatible with lockdepMarco Elver
We must avoid any recursion into lockdep if KCSAN is enabled on utilities used by lockdep. One manifestation of this is corruption of lockdep's IRQ trace state (if TRACE_IRQFLAGS), resulting in spurious warnings (see below). This commit fixes this by: 1. Using raw_local_irq{save,restore} in kcsan_setup_watchpoint(). 2. Disabling lockdep in kcsan_report(). Tested with: CONFIG_LOCKDEP=y CONFIG_DEBUG_LOCKDEP=y CONFIG_TRACE_IRQFLAGS=y This fix eliminates spurious warnings such as the following one: WARNING: CPU: 0 PID: 2 at kernel/locking/lockdep.c:4406 check_flags.part.0+0x101/0x220 Modules linked in: CPU: 0 PID: 2 Comm: kthreadd Not tainted 5.5.0-rc1+ #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:check_flags.part.0+0x101/0x220 <snip> Call Trace: lock_is_held_type+0x69/0x150 freezer_fork+0x20b/0x370 cgroup_post_fork+0x2c9/0x5c0 copy_process+0x2675/0x3b40 _do_fork+0xbe/0xa30 ? _raw_spin_unlock_irqrestore+0x40/0x50 ? match_held_lock+0x56/0x250 ? kthread_park+0xf0/0xf0 kernel_thread+0xa6/0xd0 ? kthread_park+0xf0/0xf0 kthreadd+0x321/0x3d0 ? kthread_create_on_cpu+0x130/0x130 ret_from_fork+0x3a/0x50 irq event stamp: 64 hardirqs last enabled at (63): [<ffffffff9a7995d0>] _raw_spin_unlock_irqrestore+0x40/0x50 hardirqs last disabled at (64): [<ffffffff992a96d2>] kcsan_setup_watchpoint+0x92/0x460 softirqs last enabled at (32): [<ffffffff990489b8>] fpu__copy+0xe8/0x470 softirqs last disabled at (30): [<ffffffff99048939>] fpu__copy+0x69/0x470 Reported-by: Qian Cai <cai@lca.pw> Signed-off-by: Marco Elver <elver@google.com> Acked-by: Alexander Potapenko <glider@google.com> Tested-by: Qian Cai <cai@lca.pw> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Rate-limit reporting per data racesMarco Elver
KCSAN data-race reports can occur quite frequently, so much so as to render the system useless. This commit therefore adds support for time-based rate-limiting KCSAN reports, with the time interval specified by a new KCSAN_REPORT_ONCE_IN_MS Kconfig option. The default is 3000 milliseconds, also known as three seconds. Because KCSAN must detect data races in allocators and in other contexts where use of allocation is ill-advised, a fixed-size array is used to buffer reports during each reporting interval. To reduce the number of reports lost due to array overflow, this commit stores only one instance of duplicate reports, which has the benefit of further reducing KCSAN's console output rate. Reported-by: Qian Cai <cai@lca.pw> Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Show full access type in reportMarco Elver
This commit adds access-type information to KCSAN's reports as follows: "read", "read (marked)", "write", and "write (marked)". Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Prefer __always_inline for fast-pathMarco Elver
Prefer __always_inline for fast-path functions that are called outside of user_access_save, to avoid generating UACCESS warnings when optimizing for size (CC_OPTIMIZE_FOR_SIZE). It will also avoid future surprises with compiler versions that change the inlining heuristic even when optimizing for performance. Reported-by: Randy Dunlap <rdunlap@infradead.org> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: http://lkml.kernel.org/r/58708908-84a0-0a81-a836-ad97e33dbb62@infradead.org
2020-03-21Merge branch 'linus' into locking/kcsan, to pick up fixesIngo Molnar
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21Merge branch 'x86/kdump' into locking/kcsan, to resolve conflictsIngo Molnar
Conflicts: arch/x86/purgatory/Makefile Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-20bpf: Explicitly memset some bpf info structures declared on the stackGreg Kroah-Hartman
Trying to initialize a structure with "= {};" will not always clean out all padding locations in a structure. So be explicit and call memset to initialize everything for a number of bpf information structures that are then copied from userspace, sometimes from smaller memory locations than the size of the structure. Reported-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20200320162258.GA794295@kroah.com
2020-03-20bpf: Explicitly memset the bpf_attr structureGreg Kroah-Hartman
For the bpf syscall, we are relying on the compiler to properly zero out the bpf_attr union that we copy userspace data into. Unfortunately that doesn't always work properly, padding and other oddities might not be correctly zeroed, and in some tests odd things have been found when the stack is pre-initialized to other values. Fix this by explicitly memsetting the structure to 0 before using it. Reported-by: Maciej Żenczykowski <maze@google.com> Reported-by: John Stultz <john.stultz@linaro.org> Reported-by: Alexander Potapenko <glider@google.com> Reported-by: Alistair Delva <adelva@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yhs@fb.com> Link: https://android-review.googlesource.com/c/kernel/common/+/1235490 Link: https://lore.kernel.org/bpf/20200320094813.GA421650@kroah.com
2020-03-20lockdep: Teach lockdep about "USED" <- "IN-NMI" inversionsPeter Zijlstra
nmi_enter() does lockdep_off() and hence lockdep ignores everything. And NMI context makes it impossible to do full IN-NMI tracking like we do IN-HARDIRQ, that could result in graph_lock recursion. However, since look_up_lock_class() is lockless, we can find the class of a lock that has prior use and detect IN-NMI after USED, just not USED after IN-NMI. NOTE: By shifting the lockdep_off() recursion count to bit-16, we can easily differentiate between actual recursion and off. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Link: https://lkml.kernel.org/r/20200221134215.090538203@infradead.org
2020-03-20locking/lockdep: Rework lockdep_lockPeter Zijlstra
A few sites want to assert we own the graph_lock/lockdep_lock, provide a more conventional lock interface for it with a number of trivial debug checks. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200313102107.GX12561@hirez.programming.kicks-ass.net
2020-03-20locking/lockdep: Fix bad recursion patternPeter Zijlstra
There were two patterns for lockdep_recursion: Pattern-A: if (current->lockdep_recursion) return current->lockdep_recursion = 1; /* do stuff */ current->lockdep_recursion = 0; Pattern-B: current->lockdep_recursion++; /* do stuff */ current->lockdep_recursion--; But a third pattern has emerged: Pattern-C: current->lockdep_recursion = 1; /* do stuff */ current->lockdep_recursion = 0; And while this isn't broken per-se, it is highly dangerous because it doesn't nest properly. Get rid of all Pattern-C instances and shore up Pattern-A with a warning. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200313093325.GW12561@hirez.programming.kicks-ass.net
2020-03-20locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps()Boqun Feng
Qian Cai reported a bug when PROVE_RCU_LIST=y, and read on /proc/lockdep triggered a warning: [ ] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled) ... [ ] Call Trace: [ ] lock_is_held_type+0x5d/0x150 [ ] ? rcu_lockdep_current_cpu_online+0x64/0x80 [ ] rcu_read_lock_any_held+0xac/0x100 [ ] ? rcu_read_lock_held+0xc0/0xc0 [ ] ? __slab_free+0x421/0x540 [ ] ? kasan_kmalloc+0x9/0x10 [ ] ? __kmalloc_node+0x1d7/0x320 [ ] ? kvmalloc_node+0x6f/0x80 [ ] __bfs+0x28a/0x3c0 [ ] ? class_equal+0x30/0x30 [ ] lockdep_count_forward_deps+0x11a/0x1a0 The warning got triggered because lockdep_count_forward_deps() call __bfs() without current->lockdep_recursion being set, as a result a lockdep internal function (__bfs()) is checked by lockdep, which is unexpected, and the inconsistency between the irq-off state and the state traced by lockdep caused the warning. Apart from this warning, lockdep internal functions like __bfs() should always be protected by current->lockdep_recursion to avoid potential deadlocks and data inconsistency, therefore add the current->lockdep_recursion on-and-off section to protect __bfs() in both lockdep_count_forward_deps() and lockdep_count_backward_deps() Reported-by: Qian Cai <cai@lca.pw> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200312151258.128036-1-boqun.feng@gmail.com
2020-03-20perf/core: Fix reversed NULL check in perf_event_groups_less()Dan Carpenter
This NULL check is reversed so it leads to a Smatch warning and presumably a NULL dereference. kernel/events/core.c:1598 perf_event_groups_less() error: we previously assumed 'right->cgrp->css.cgroup' could be null (see line 1590) Fixes: 95ed6c707f26 ("perf/cgroup: Order events in RB tree by cgroup id") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200312105637.GA8960@mwanda
2020-03-20perf/core: Fix endless multiplex timerPeter Zijlstra
Kan and Andi reported that we fail to kill rotation when the flexible events go empty, but the context does not. XXX moar Fixes: fd7d55172d1e ("perf/cgroups: Don't rotate events for cgroups unnecessarily") Reported-by: Andi Kleen <ak@linux.intel.com> Reported-by: Kan Liang <kan.liang@linux.intel.com> Tested-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200305123851.GX2596@hirez.programming.kicks-ass.net
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