- 14 Jun, 2018 2 commits
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Mark Rutland authored
During a context switch, we first switch_mm() to the next task's mm, then switch_to() that new task. This means that vmalloc'd regions which had previously been faulted in can transiently disappear in the context of the prev task. Functions instrumented by KCOV may try to access a vmalloc'd kcov_area during this window, and as the fault handling code is instrumented, this results in a recursive fault. We must avoid accessing any kcov_area during this window. We can do so with a new flag in kcov_mode, set prior to switching the mm, and cleared once the new task is live. Since task_struct::kcov_mode isn't always a specific enum kcov_mode value, this is made an unsigned int. The manipulation is hidden behind kcov_{prepare,finish}_switch() helpers, which are empty for !CONFIG_KCOV kernels. The code uses macros because I can't use static inline functions without a circular include dependency between <linux/sched.h> and <linux/kcov.h>, since the definition of task_struct uses things defined in <linux/kcov.h> Link: http://lkml.kernel.org/r/20180504135535.53744-4-mark.rutland@arm.com Signed-off-by:Mark Rutland <mark.rutland@arm.com> Acked-by:
Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds authored
The changes to automatically test for working stack protector compiler support in the Kconfig files removed the special STACKPROTECTOR_AUTO option that picked the strongest stack protector that the compiler supported. That was all a nice cleanup - it makes no sense to have the AUTO case now that the Kconfig phase can just determine the compiler support directly. HOWEVER. It also meant that doing "make oldconfig" would now _disable_ the strong stackprotector if you had AUTO enabled, because in a legacy config file, the sane stack protector configuration would look like CONFIG_HAVE_CC_STACKPROTECTOR=y # CONFIG_CC_STACKPROTECTOR_NONE is not set # CONFIG_CC_STACKPROTECTOR_REGULAR is not set # CONFIG_CC_STACKPROTECTOR_STRONG is not set CONFIG_CC_STACKPROTECTOR_AUTO=y and when you ran this through "make oldconfig" with the Kbuild changes, it would ask you about the regular CONFIG_CC_STACKPROTECTOR (that had been renamed from CONFIG_CC_STACKPROTECTOR_REGULAR to just CONFIG_CC_STACKPROTECTOR), but it would think that the STRONG version used to be disabled (because it was really enabled by AUTO), and would disable it in the new config, resulting in: CONFIG_HAVE_CC_STACKPROTECTOR=y CONFIG_CC_HAS_STACKPROTECTOR_NONE=y CONFIG_CC_STACKPROTECTOR=y # CONFIG_CC_STACKPROTECTOR_STRONG is not set CONFIG_CC_HAS_SANE_STACKPROTECTOR=y That's dangerously subtle - people could suddenly find themselves with the weaker stack protector setup without even realizing. The solution here is to just rename not just the old RECULAR stack protector option, but also the strong one. This does that by just removing the CC_ prefix entirely for the user choices, because it really is not about the compiler support (the compiler support now instead automatially impacts _visibility_ of the options to users). This results in "make oldconfig" actually asking the user for their choice, so that we don't have any silent subtle security model changes. The end result would generally look like this: CONFIG_HAVE_CC_STACKPROTECTOR=y CONFIG_CC_HAS_STACKPROTECTOR_NONE=y CONFIG_STACKPROTECTOR=y CONFIG_STACKPROTECTOR_STRONG=y CONFIG_CC_HAS_SANE_STACKPROTECTOR=y where the "CC_" versions really are about internal compiler infrastructure, not the user selections. Acked-by:
Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by:
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- 06 Jun, 2018 1 commit
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Mathieu Desnoyers authored
Expose a new system call allowing each thread to register one userspace memory area to be used as an ABI between kernel and user-space for two purposes: user-space restartable sequences and quick access to read the current CPU number value from user-space. * Restartable sequences (per-cpu atomics) Restartables sequences allow user-space to perform update operations on per-cpu data without requiring heavy-weight atomic operations. The restartable critical sections (percpu atomics) work has been started by Paul Turner and Andrew Hunter. It lets the kernel handle restart of critical sections. [1] [2] The re-implementation proposed here brings a few simplifications to the ABI which facilitates porting to other architectures and speeds up the user-space fast path. Here are benchmarks of various rseq use-cases. Test hardware: arm32: ARMv7 Processor rev 4 (v7l) "Cubietruck", 2-core x86-64: Intel E5-2630 v3@2.40GHz, 16-core, hyperthreading The following benchmarks were all performed on a single thread. * Per-CPU statistic counter increment getcpu+atomic (ns/op) rseq (ns/op) speedup arm32: 344.0 31.4 11.0 x86-64: 15.3 2.0 7.7 * LTTng-UST: write event 32-bit header, 32-bit payload into tracer per-cpu buffer getcpu+atomic (ns/op) rseq (ns/op) speedup arm32: 2502.0 2250.0 1.1 x86-64: 117.4 98.0 1.2 * liburcu percpu: lock-unlock pair, dereference, read/compare word getcpu+atomic (ns/op) rseq (ns/op) speedup arm32: 751.0 128.5 5.8 x86-64: 53.4 28.6 1.9 * jemalloc memory allocator adapted to use rseq Using rseq with per-cpu memory pools in jemalloc at Facebook (based on rseq 2016 implementation): The production workload response-time has 1-2% gain avg. latency, and the P99 overall latency drops by 2-3%. * Reading the current CPU number Speeding up reading the current CPU number on which the caller thread is running is done by keeping the current CPU number up do date within the cpu_id field of the memory area registered by the thread. This is done by making scheduler preemption set the TIF_NOTIFY_RESUME flag on the current thread. Upon return to user-space, a notify-resume handler updates the current CPU value within the registered user-space memory area. User-space can then read the current CPU number directly from memory. Keeping the current cpu id in a memory area shared between kernel and user-space is an improvement over current mechanisms available to read the current CPU number, which has the following benefits over alternative approaches: - 35x speedup on ARM vs system call through glibc - 20x speedup on x86 compared to calling glibc, which calls vdso executing a "lsl" instruction, - 14x speedup on x86 compared to inlined "lsl" instruction, - Unlike vdso approaches, this cpu_id value can be read from an inline assembly, which makes it a useful building block for restartable sequences. - The approach of reading the cpu id through memory mapping shared between kernel and user-space is portable (e.g. ARM), which is not the case for the lsl-based x86 vdso. On x86, yet another possible approach would be to use the gs segment selector to point to user-space per-cpu data. This approach performs similarly to the cpu id cache, but it has two disadvantages: it is not portable, and it is incompatible with existing applications already using the gs segment selector for other purposes. Benchmarking various approaches for reading the current CPU number: ARMv7 Processor rev 4 (v7l) Machine model: Cubietruck - Baseline (empty loop): 8.4 ns - Read CPU from rseq cpu_id: 16.7 ns - Read CPU from rseq cpu_id (lazy register): 19.8 ns - glibc 2.19-0ubuntu6.6 getcpu: 301.8 ns - getcpu system call: 234.9 ns x86-64 Intel(R) Xeon(R) CPU E5-2630 v3 @ 2.40GHz: - Baseline (empty loop): 0.8 ns - Read CPU from rseq cpu_id: 0.8 ns - Read CPU from rseq cpu_id (lazy register): 0.8 ns - Read using gs segment selector: 0.8 ns - "lsl" inline assembly: 13.0 ns - glibc 2.19-0ubuntu6 getcpu: 16.6 ns - getcpu system call: 53.9 ns - Speed (benchmark taken on v8 of patchset) Running 10 runs of hackbench -l 100000 seems to indicate, contrary to expectations, that enabling CONFIG_RSEQ slightly accelerates the scheduler: Configuration: 2 sockets * 8-core Intel(R) Xeon(R) CPU E5-2630 v3 @ 2.40GHz (directly on hardware, hyperthreading disabled in BIOS, energy saving disabled in BIOS, turboboost disabled in BIOS, cpuidle.off=1 kernel parameter), with a Linux v4.6 defconfig+localyesconfig, restartable sequences series applied. * CONFIG_RSEQ=n avg.: 41.37 s std.dev.: 0.36 s * CONFIG_RSEQ=y avg.: 40.46 s std.dev.: 0.33 s - Size On x86-64, between CONFIG_RSEQ=n/y, the text size increase of vmlinux is 567 bytes, and the data size increase of vmlinux is 5696 bytes. [1] https://lwn.net/Articles/650333/ [2] http://www.linuxplumbersconf.org/2013/ocw/system/presentations/1695/original/LPC%20-%20PerCpu%20Atomics.pdf Signed-off-by:Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Acked-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Joel Fernandes <joelaf@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dave Watson <davejwatson@fb.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: Chris Lameter <cl@linux.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: Andrew Hunter <ahh@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com> Cc: Paul Turner <pjt@google.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ben Maurer <bmaurer@fb.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-api@vger.kernel.org Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20151027235635.16059.11630.stgit@pjt-glaptop.roam.corp.google.com Link: http://lkml.kernel.org/r/20150624222609.6116.86035.stgit@kitami.mtv.corp.google.com Link: https://lkml.kernel.org/r/20180602124408.8430-3-mathieu.desnoyers@efficios.com
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- 25 May, 2018 1 commit
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Dave Martin authored
There are a number of bits of code sprinkled around the kernel to set a thread flag if a certain condition is true, and clear it otherwise. To help make those call sites terser and less cumbersome, this patch adds a new family of thread flag manipulators update*_thread_flag([...,] flag, cond) which do the equivalent of: if (cond) set*_thread_flag([...,] flag); else clear*_thread_flag([...,] flag); Signed-off-by:
Dave Martin <Dave.Martin@arm.com> Reviewed-by:
Alex Bennée <alex.bennee@linaro.org> Acked-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Acked-by:
Marc Zyngier <marc.zyngier@arm.com> Acked-by:
Catalin Marinas <catalin.marinas@arm.com> Acked-by:
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- 15 May, 2018 1 commit
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Paul E. McKenney authored
The cond_resched_softirq() macro is not used anywhere in mainline, so this commit simplifies the kernel by eliminating it. Suggested-by:
Eric Dumazet <edumazet@google.com> Signed-off-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@redhat.com> Acked-by:
Nicholas Piggin <npiggin@gmail.com>
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- 14 May, 2018 1 commit
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Rohit Jain authored
sched/core: Distinguish between idle_cpu() calls based on desired effect, introduce available_idle_cpu() In the following commit: 247f2f6f ("sched/core: Don't schedule threads on pre-empted vCPUs") ... we distinguish between idle_cpu() when the vCPU is not running for scheduling threads. However, the idle_cpu() function is used in other places for actually checking whether the state of the CPU is idle or not. Hence split the use of that function based on the desired return value, by introducing the available_idle_cpu() function. This fixes a (slight) regression in that initial vCPU commit, because some code paths (like the load-balancer) don't care and shouldn't care if the vCPU is preempted or not, they just want to know if there's any tasks on the CPU. Signed-off-by:
Rohit Jain <rohit.k.jain@oracle.com> Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- 04 May, 2018 2 commits
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Thomas Gleixner authored
For certain use cases it is desired to enforce mitigations so they cannot be undone afterwards. That's important for loader stubs which want to prevent a child from disabling the mitigation again. Will also be used for seccomp(). The extra state preserving of the prctl state for SSB is a preparatory step for EBPF dymanic speculation control. Signed-off-by: -
Peter Zijlstra authored
Gaurav reported a perceived problem with TASK_PARKED, which turned out to be a broken wait-loop pattern in __kthread_parkme(), but the reported issue can (and does) in fact happen for states that do not do condition based sleeps. When the 'current->state = TASK_RUNNING' store of a previous (concurrent) try_to_wake_up() collides with the setting of a 'special' sleep state, we can loose the sleep state. Normal condition based wait-loops are immune to this problem, but for sleep states that are not condition based are subject to this problem. There already is a fix for TASK_DEAD. Abstract that and also apply it to TASK_STOPPED and TASK_TRACED, both of which are also without condition based wait-loop. Reported-by:
Gaurav Kohli <gkohli@codeaurora.org> Signed-off-by:
Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
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- 05 Apr, 2018 1 commit
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Peter Zijlstra authored
For some as yet not understood reason, Tony gets unaligned access traps on IA64 because of: struct util_est ue = READ_ONCE(p->se.avg.util_est); and: WRITE_ONCE(p->se.avg.util_est, ue); introduced by commit: d519329f ("sched/fair: Update util_est only on util_avg updates") Normally those two fields should end up on an 8-byte aligned location, but UP and RANDSTRUCT can mess that up so enforce the alignment explicitly. Also make the alignment on sched_avg unconditional, as it is really about data locality, not false-sharing. With or without this patch the layout for sched_avg on a ia64-defconfig build looks like: $ pahole -EC sched_avg ia64-defconfig/kernel/sched/core.o die__process_function: tag not supported (INVALID)! struct sched_avg { /* typedef u64 */ long long unsigned int last_update_time; /* 0 8 */ /* typedef u64 */ long long unsigned int load_sum; /* 8 8 */ /* typedef u64 */ long long unsigned int runnable_load_sum; /* 16 8 */ /* typedef u32 */ unsigned int util_sum; /* 24 4 */ /* typedef u32 */ unsigned int period_contrib; /* 28 4 */ long unsigned int load_avg; /* 32 8 */ long unsigned int runnable_load_avg; /* 40 8 */ long unsigned int util_avg; /* 48 8 */ struct util_est { unsigned int enqueued; /* 56 4 */ unsigned int ewma; /* 60 4 */ } util_est; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ /* size: 64, cachelines: 1, members: 9 */ }; Reported-and-Tested-by:
Tony Luck <tony.luck@intel.com> Signed-off-by:
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- 20 Mar, 2018 1 commit
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Patrick Bellasi authored
The util_avg signal computed by PELT is too variable for some use-cases. For example, a big task waking up after a long sleep period will have its utilization almost completely decayed. This introduces some latency before schedutil will be able to pick the best frequency to run a task. The same issue can affect task placement. Indeed, since the task utilization is already decayed at wakeup, when the task is enqueued in a CPU, this can result in a CPU running a big task as being temporarily represented as being almost empty. This leads to a race condition where other tasks can be potentially allocated on a CPU which just started to run a big task which slept for a relatively long period. Moreover, the PELT utilization of a task can be updated every [ms], thus making it a continuously changing value for certain longer running tasks. This means that the instantaneous PELT utilization of a RUNNING task is not really meaningful to properly support scheduler decisions. For all these reasons, a more stable signal can do a better job of representing the expected/estimated utilization of a task/cfs_rq. Such a signal can be easily created on top of PELT by still using it as an estimator which produces values to be aggregated on meaningful events. This patch adds a simple implementation of util_est, a new signal built on top of PELT's util_avg where: util_est(task) = max(task::util_avg, f(task::util_avg@dequeue)) This allows to remember how big a task has been reported by PELT in its previous activations via f(task::util_avg@dequeue), which is the new _task_util_est(struct task_struct*) function added by this patch. If a task should change its behavior and it runs longer in a new activation, after a certain time its util_est will just track the original PELT signal (i.e. task::util_avg). The estimated utilization of cfs_rq is defined only for root ones. That's because the only sensible consumer of this signal are the scheduler and schedutil when looking for the overall CPU utilization due to FAIR tasks. For this reason, the estimated utilization of a root cfs_rq is simply defined as: util_est(cfs_rq) = max(cfs_rq::util_avg, cfs_rq::util_est::enqueued) where: cfs_rq::util_est::enqueued = sum(_task_util_est(task)) for each RUNNABLE task on that root cfs_rq It's worth noting that the estimated utilization is tracked only for objects of interests, specifically: - Tasks: to better support tasks placement decisions - root cfs_rqs: to better support both tasks placement decisions as well as frequencies selection Signed-off-by:Patrick Bellasi <patrick.bellasi@arm.com> Signed-off-by:
Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Steve Muckle <smuckle@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Todd Kjos <tkjos@android.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Link: http://lkml.kernel.org/r/20180309095245.11071-2-patrick.bellasi@arm.com
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- 12 Mar, 2018 1 commit
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Peter Zijlstra authored
It's unused: $ git grep "\<TASK_ALL\>" | wc -l 1 ... and it is also dangerous, kill the bugger. Signed-off-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by:
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- 07 Feb, 2018 1 commit
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Mike Rapoport authored
There are several functions that do find_task_by_vpid() followed by get_task_struct(). We can use a helper function instead. Link: http://lkml.kernel.org/r/1509602027-11337-1-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by:
Mike Rapoport <rppt@linux.vnet.ibm.com> Acked-by:
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- 06 Feb, 2018 1 commit
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Mel Gorman authored
The select_idle_sibling() (SIS) rewrite in commit: 10e2f1ac ("sched/core: Rewrite and improve select_idle_siblings()") ... replaced a domain iteration with a search that broadly speaking does a wrapped walk of the scheduler domain sharing a last-level-cache. While this had a number of improvements, one consequence is that two tasks that share a waker/wakee relationship push each other around a socket. Even though two tasks may be active, all cores are evenly used. This is great from a search perspective and spreads a load across individual cores, but it has adverse consequences for cpufreq. As each CPU has relatively low utilisation, cpufreq may decide the utilisation is too low to used a higher P-state and overall computation throughput suffers. While individual cpufreq and cpuidle drivers may compensate by artifically boosting P-state (at c0) or avoiding lower C-states (during idle), it does not help if hardware-based cpufreq (e.g. HWP) is used. This patch tracks a recently used CPU based on what CPU a task was running on when it last was a waker a CPU it was recently using when a task is a wakee. During SIS, the recently used CPU is used as a target if it's still allowed by the task and is idle. The benefit may be non-obvious so consider an example of two tasks communicating back and forth. Task A may be an application doing IO where task B is a kworker or kthread like journald. Task A may issue IO, wake B and B wakes up A on completion. With the existing scheme this may look like the following (potentially different IDs if SMT is in use but similar principal applies). A (cpu 0) wake B (wakes on cpu 1) B (cpu 1) wake A (wakes on cpu 2) A (cpu 2) wake B (wakes on cpu 3) etc. A careful reader may wonder why CPU 0 was not idle when B wakes A the first time and it's simply due to the fact that A can be rescheduled to another CPU and the pattern is that prev == target when B tries to wakeup A and the information about CPU 0 has been lost. With this patch, the pattern is more likely to be: A (cpu 0) wake B (wakes on cpu 1) B (cpu 1) wake A (wakes on cpu 0) A (cpu 0) wake B (wakes on cpu 1) etc i.e. two communicating casts are more likely to use just two cores instead of all available cores sharing a LLC. The most dramatic speedup was noticed on dbench using the XFS filesystem on UMA as clients interact heavily with workqueues in that configuration. Note that a similar speedup is not observed on ext4 as the wakeup pattern is different: 4.15.0-rc9 4.15.0-rc9 waprev-v1 biasancestor-v1 Hmean 1 287.54 ( 0.00%) 817.01 ( 184.14%) Hmean 2 1268.12 ( 0.00%) 1781.24 ( 40.46%) Hmean 4 1739.68 ( 0.00%) 1594.47 ( -8.35%) Hmean 8 2464.12 ( 0.00%) 2479.56 ( 0.63%) Hmean 64 1455.57 ( 0.00%) 1434.68 ( -1.44%) The results can be less dramatic on NUMA where automatic balancing interferes with the test. It's also known that network benchmarks running on localhost also benefit quite a bit from this patch (roughly 10% on netperf RR for UDP and TCP depending on the machine). Hackbench also seens small improvements (6-11% depending on machine and thread count). The facebook schbench was also tested but in most cases showed little or no different to wakeup latencies. Signed-off-by:
Mel Gorman <mgorman@techsingularity.net> Signed-off-by:
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- 10 Jan, 2018 2 commits
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Juri Lelli authored
Worker kthread needs to be able to change frequency for all other threads. Make it special, just under STOP class. Signed-off-by:
Juri Lelli <juri.lelli@arm.com> Signed-off-by:
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Juri Lelli authored
This patch adds the possibility of getting the delivery of a SIGXCPU signal whenever there is a runtime overrun. The request is done through the sched_flags field within the sched_attr structure. Forward port of https://lkml.org/lkml/2009/10/16/170 Tested-by:
Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by:
Juri Lelli <juri.lelli@gmail.com> Signed-off-by:
Claudio Scordino <claudio@evidence.eu.com> Signed-off-by:
Luca Abeni <luca.abeni@santannapisa.it> Signed-off-by:
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- 09 Jan, 2018 1 commit
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David Howells authored
Construct the init thread stack in the linker script rather than doing it by means of a union so that ia64's init_task.c can be got rid of. The following symbols are then made available from INIT_TASK_DATA() linker script macro: init_thread_union init_stack INIT_TASK_DATA() also expands the region to THREAD_SIZE to accommodate the size of the init stack. init_thread_union is given its own section so that it can be placed into the stack space in the right order. I'm assuming that the ia64 ordering is correct and that the task_struct is first and the thread_info second. Signed-off-by:
David Howells <dhowells@redhat.com> Tested-by:
Palmer Dabbelt <palmer@sifive.com> Acked-by:
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- 15 Dec, 2017 1 commit
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Arnd Bergmann authored
gcc-8 warns about using strncpy() with the source size as the limit: fs/exec.c:1223:32: error: argument to 'sizeof' in 'strncpy' call is the same expression as the source; did you mean to use the size of the destination? [-Werror=sizeof-pointer-memaccess] This is indeed slightly suspicious, as it protects us from source arguments without NUL-termination, but does not guarantee that the destination is terminated. This keeps the strncpy() to ensure we have properly padded target buffer, but ensures that we use the correct length, by passing the actual length of the destination buffer as well as adding a build-time check to ensure it is exactly TASK_COMM_LEN. There are only 23 callsites which I all reviewed to ensure this is currently the case. We could get away with doing only the check or passing the right length, but it doesn't hurt to do both. Link: http://lkml.kernel.org/r/20171205151724.1764896-1-arnd@arndb.de Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Suggested-by:
Kees Cook <keescook@chromium.org> Acked-by:
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- 12 Dec, 2017 1 commit
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Ingo Molnar authored
This code (CONFIG_LOCKDEP_CROSSRELEASE=y and CONFIG_LOCKDEP_COMPLETIONS=y), while it found a number of old bugs initially, was also causing too many false positives that caused people to disable lockdep - which is arguably a worse overall outcome. If we disable cross-release by default but keep the code upstream then in practice the most likely outcome is that we'll allow the situation to degrade gradually, by allowing entropy to introduce more and more false positives, until it overwhelms maintenance capacity. Another bad side effect was that people were trying to work around the false positives by uglifying/complicating unrelated code. There's a marked difference between annotating locking operations and uglifying good code just due to bad lock debugging code ... This gradual decrease in quality happened to a number of debugging facilities in the kernel, and lockdep is pretty complex already, so we cannot risk this outcome. Either cross-releas...
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- 21 Nov, 2017 1 commit
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Dan Carpenter authored
It doesn't cause a run-time bug, but these bitfields should be unsigned. When it's signed ->dl_throttled is set to either 0 or -1, instead of 0 and 1 as expected. The sched.h file is included into tons of places so Sparse generates a flood of warnings like this: ./include/linux/sched.h:477:54: error: dubious one-bit signed bitfield Reported-by:
Matthew Wilcox <willy@infradead.org> Reported-by:
Xin Long <lucien.xin@gmail.com> Signed-off-by:
Dan Carpenter <dan.carpenter@oracle.com> Reviewed-by:
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- 02 Nov, 2017 1 commit
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Greg Kroah-Hartman authored
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by:
Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by:
Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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- 27 Oct, 2017 1 commit
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Frederic Weisbecker authored
We want to centralize the isolation features, to be done by the housekeeping subsystem and scheduler domain isolation is a significant part of it. No intended behaviour change, we just reuse the housekeeping cpumask and core code. Signed-off-by:
Frederic Weisbecker <frederic@kernel.org> Acked-by:
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- 10 Oct, 2017 2 commits
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luca abeni authored
Ask the compiler to use a single bit for storing true / false values, instead of wasting the size of a whole int value. Tested with gcc 5.4.0 on x86_64, and the compiler produces the expected Assembly (similar to the Assembly code generated when explicitly accessing the bits with bitmasks, "&" and "|"). Signed-off-by:
Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1504778971-13573-5-git-send-email-luca.abeni@santannapisa.it Signed-off-by:
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Peter Zijlstra authored
Steve requested better names for the new task-state helper functions. So introduce the concept of task-state index for the printing and rename __get_task_state() to task_state_index() and __task_state_to_char() to task_index_to_char(). Requested-by:
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- 29 Sep, 2017 7 commits
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Peter Zijlstra authored
The load balancer uses runnable_load_avg as load indicator. For !cgroup this is: runnable_load_avg = \Sum se->avg.load_avg ; where se->on_rq That is, a direct sum of all runnable tasks on that runqueue. As opposed to load_avg, which is a sum of all tasks on the runqueue, which includes a blocked component. However, in the cgroup case, this comes apart since the group entities are always runnable, even if most of their constituent entities are blocked. Therefore introduce a runnable_weight which for task entities is the same as the regular weight, but for group entities is a fraction of the entity weight and represents the runnable part of the group runqueue. Then propagate this load through the PELT hierarchy to arrive at an effective runnable load avgerage -- which we should not confuse with the canonical runnable load average. Suggested-by:
Tejun Heo <tj@kernel.org> Signed-off-by:
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Peter Zijlstra authored
Currently TASK_PARKED is masqueraded as TASK_INTERRUPTIBLE, give it its own print state because it will not in fact get woken by regular wakeups and is a long-term state. This requires moving TASK_PARKED into the TASK_REPORT mask, and since that latter needs to be a contiguous bitmask, we need to shuffle the bits around a bit. Signed-off-by:
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Peter Zijlstra authored
Markus reported that kthreads that idle using TASK_IDLE instead of TASK_INTERRUPTIBLE are reported in as TASK_UNINTERRUPTIBLE and things like htop mark those red. This is undesirable, so add an explicit state for TASK_IDLE. Reported-by:
Markus Trippelsdorf <markus@trippelsdorf.de> Signed-off-by:
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Peter Zijlstra authored
Remove yet another task-state char instance. Signed-off-by:
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Peter Zijlstra authored
Convert trace_sched_switch to use the common task-state helpers and fix the "X" and "Z" order, possibly they ended up in the wrong order because TASK_REPORT has them in the wrong order too. Signed-off-by:
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Peter Zijlstra authored
Bit patterns are easier in hex. Signed-off-by:
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Peter Zijlstra authored
Currently get_task_state() and task_state_to_char() report different states, create a number of common helpers and unify the reported state space. Signed-off-by:
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- 09 Sep, 2017 1 commit
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Davidlohr Bueso authored
... with the generic rbtree flavor instead. No changes in semantics whatsoever. Link: http://lkml.kernel.org/r/20170719014603.19029-10-dave@stgolabs.net Signed-off-by:
Davidlohr Bueso <dbueso@suse.de> Acked-by:
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- 21 Aug, 2017 1 commit
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Oleg Nesterov authored
This was reported many times, and this was even mentioned in commit 52ee2dfd ("pids: refactor vnr/nr_ns helpers to make them safe") but somehow nobody bothered to fix the obvious problem: task_tgid_nr_ns() is not safe because task->group_leader points to nowhere after the exiting task passes exit_notify(), rcu_read_lock() can not help. We really need to change __unhash_process() to nullify group_leader, parent, and real_parent, but this needs some cleanups. Until then we can turn task_tgid_nr_ns() into another user of __task_pid_nr_ns() and fix the problem. Reported-by:
Troy Kensinger <tkensinger@google.com> Signed-off-by:
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- 17 Aug, 2017 1 commit
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Paul E. McKenney authored
Currently, the exit-time support for TASKS_RCU is open-coded in do_exit(). This commit creates exit_tasks_rcu_start() and exit_tasks_rcu_finish() APIs for do_exit() use. This has the benefit of confining the use of the tasks_rcu_exit_srcu variable to one file, allowing it to become static. Signed-off-by:
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- 10 Aug, 2017 4 commits
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Byungchul Park authored
The ring buffer can be overwritten by hardirq/softirq/work contexts. That cases must be considered on rollback or commit. For example, |<------ hist_lock ring buffer size ----->| ppppppppppppiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii wrapped > iiiiiiiiiiiiiiiiiiiiiii.................... where 'p' represents an acquisition in process context, 'i' represents an acquisition in irq context. On irq exit, crossrelease tries to rollback idx to original position, but it should not because the entry already has been invalid by overwriting 'i'. Avoid rollback or commit for entries overwritten. Signed-off-by:Byungchul Park <byungchul.park@lge.com> Signed-off-by:
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Byungchul Park authored
Lockdep is a runtime locking correctness validator that detects and reports a deadlock or its possibility by checking dependencies between locks. It's useful since it does not report just an actual deadlock but also the possibility of a deadlock that has not actually happened yet. That enables problems to be fixed before they affect real systems. However, this facility is only applicable to typical locks, such as spinlocks and mutexes, which are normally released within the context in which they were acquired. However, synchronization primitives like page locks or completions, which are allowed to be released in any context, also create dependencies and can cause a deadlock. So lockdep should track these locks to do a better job. The 'crossrelease' implementation makes these primitives also be tracked. Signed-off-by:
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Peter Zijlstra authored
A while ago someone, and I cannot find the email just now, asked if we could not implement the RECLAIM_FS inversion stuff with a 'fake' lock like we use for other things like workqueues etc. I think this should be possible which allows reducing the 'irq' states and will reduce the amount of __bfs() lookups we do. Removing the 1 IRQ state results in 4 less __bfs() walks per dependency, improving lockdep performance. And by moving this annotation out of the lockdep code it becomes easier for the mm people to extend. Signed-off-by:
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Xie XiuQi authored
Now that we have more than one place to get the task state, intruduce the task_state_to_char() helper function to save some code. No functionality changed. Signed-off-by:
Xie XiuQi <xiexiuqi@huawei.com> Signed-off-by:
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- 01 Aug, 2017 3 commits
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Vikas Shivappa authored
The root directory, ctrl_mon and monitor groups are populated with a read/write file named "tasks". When read, it shows all the task IDs assigned to the resource group. Tasks can be added to groups by writing the PID to the file. A task can be present in one "ctrl_mon" group "and" one "monitor" group. IOW a PID_x can be seen in a ctrl_mon group and a monitor group at the same time. When a task is added to a ctrl_mon group, it is automatically removed from the previous ctrl_mon group where it belonged. Similarly if a task is moved to a monitor group it is removed from the previous monitor group . Also since the monitor groups can only have subset of tasks of parent ctrl_mon group, a task can be moved to a monitor group only if its already present in the parent ctrl_mon group. Task membership is indicated by a new field in the task_struct "u32 rmid" which holds the RMID for the task. RMID=0 is reserved for the default root group where the tasks belong to at mount. [tony: zero the rmid if rdtgroup was deleted when task was being moved] Signed-off-by:
Tony Luck <tony.luck@linux.intel.com> Signed-off-by:
Vikas Shivappa <vikas.shivappa@linux.intel.com> Signed-off-by:
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Vikas Shivappa authored
OS associates a CLOSid(Class of service id) to a task by writing the high 32 bits of per CPU IA32_PQR_ASSOC MSR when a task is scheduled in. CPUID.(EAX=10H, ECX=1):EDX[15:0] enumerates the max CLOSID supported and it is zero indexed. Hence change the type to u32 from int. Signed-off-by:
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Vikas Shivappa authored
We currently have a CONFIG_RDT_A which is for RDT(Resource directory technology) allocation based resctrl filesystem interface. As a preparation to add support for RDT monitoring as well into the same resctrl filesystem, change the config option to be CONFIG_RDT which would include both RDT allocation and monitoring code. No functional change. Signed-off-by:
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