lwn.git/kernel, branch doc/4.4

Merge branch 'akpm' (patches from Andrew)

2015-09-12T02:34:09+00:00

Merge fourth patch-bomb from Andrew Morton: - sys_membarier syscall - seq_file interface changes - a few misc fixups * emailed patches from Andrew Morton : revert "ocfs2/dlm: use list_for_each_entry instead of list_for_each" mm/early_ioremap: add explicit #include of asm/early_ioremap.h fs/seq_file: convert int seq_vprint/seq_printf/etc... returns to void selftests: enhance membarrier syscall test selftests: add membarrier syscall test sys_membarrier(): system-wide memory barrier (generic, x86) MODSIGN: fix a compilation warning in extract-cert

Merge tag 'pm+acpi-4.3-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2015-09-12T02:11:06+00:00

Pull more power management and ACPI updates from Rafael Wysocki: "These are mostly fixes and cleanups on top of the previous PM+ACPI pull request (cpufreq core and drivers, cpuidle, generic power domains framework). Some of them didn't make to that pull request and some fix issues introduced by it. The only really new thing is the support for suspend frequency in the cpufreq-dt driver, but it is needed to fix an issue with Exynos platforms. Specifics: - build fix for the new Mediatek MT8173 cpufreq driver (Guenter Roeck). - generic power domains framework fixes (power on error code path, subdomain removal) and cleanup of a deprecated API user (Geert Uytterhoeven, Jon Hunter, Ulf Hansson). - cpufreq-dt driver fixes including two fixes for bugs related to the new Operating Performance Points Device Tree bindings introduced recently (Viresh Kumar). - suspend frequency support for the cpufreq-dt driver (Bartlomiej Zolnierkiewicz, Viresh Kumar). - cpufreq core cleanups (Viresh Kumar). - intel_pstate driver fixes (Chen Yu, Kristen Carlson Accardi). - additional sanity check in the cpuidle core (Xunlei Pang). - fix for a comment related to CPU power management (Lina Iyer)" * tag 'pm+acpi-4.3-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: intel_pstate: fix PCT_TO_HWP macro intel_pstate: Fix user input of min/max to legal policy region PM / OPP: Return suspend_opp only if it is enabled cpufreq-dt: add suspend frequency support cpufreq: allow cpufreq_generic_suspend() to work without suspend frequency PM / OPP: add dev_pm_opp_get_suspend_opp() helper staging: board: Migrate away from __pm_genpd_name_add_device() cpufreq: Use __func__ to print function's name cpufreq: staticize cpufreq_cpu_get_raw() PM / Domains: Ensure subdomain is not in use before removing cpufreq: Add ARM_MT8173_CPUFREQ dependency on THERMAL cpuidle/coupled: Add sanity check for safe_state_index PM / Domains: Try power off masters in error path of __pm_genpd_poweron() cpufreq: dt: Tolerance applies on both sides of target voltage cpufreq: dt: Print error on failing to mark OPPs as shared cpufreq: dt: Check OPP count before marking them shared kernel/cpu_pm: fix cpu_cluster_pm_exit comment

sys_membarrier(): system-wide memory barrier (generic, x86)

2015-09-11T22:21:34+00:00

Here is an implementation of a new system call, sys_membarrier(), which executes a memory barrier on all threads running on the system. It is implemented by calling synchronize_sched(). It can be used to distribute the cost of user-space memory barriers asymmetrically by transforming pairs of memory barriers into pairs consisting of sys_membarrier() and a compiler barrier. For synchronization primitives that distinguish between read-side and write-side (e.g. userspace RCU [1], rwlocks), the read-side can be accelerated significantly by moving the bulk of the memory barrier overhead to the write-side. The existing applications of which I am aware that would be improved by this system call are as follows: * Through Userspace RCU library (http://urcu.so) - DNS server (Knot DNS) https://www.knot-dns.cz/ - Network sniffer (http://netsniff-ng.org/) - Distributed object storage (https://sheepdog.github.io/sheepdog/) - User-space tracing (http://lttng.org) - Network storage system (https://www.gluster.org/) - Virtual routers (https://events.linuxfoundation.org/sites/events/files/slides/DPDK_RCU_0MQ.pdf) - Financial software (https://lkml.org/lkml/2015/3/23/189) Those projects use RCU in userspace to increase read-side speed and scalability compared to locking. Especially in the case of RCU used by libraries, sys_membarrier can speed up the read-side by moving the bulk of the memory barrier cost to synchronize_rcu(). * Direct users of sys_membarrier - core dotnet garbage collector (https://github.com/dotnet/coreclr/issues/198) Microsoft core dotnet GC developers are planning to use the mprotect() side-effect of issuing memory barriers through IPIs as a way to implement Windows FlushProcessWriteBuffers() on Linux. They are referring to sys_membarrier in their github thread, specifically stating that sys_membarrier() is what they are looking for. To explain the benefit of this scheme, let's introduce two example threads: Thread A (non-frequent, e.g. executing liburcu synchronize_rcu()) Thread B (frequent, e.g. executing liburcu rcu_read_lock()/rcu_read_unlock()) In a scheme where all smp_mb() in thread A are ordering memory accesses with respect to smp_mb() present in Thread B, we can change each smp_mb() within Thread A into calls to sys_membarrier() and each smp_mb() within Thread B into compiler barriers "barrier()". Before the change, we had, for each smp_mb() pairs: Thread A Thread B previous mem accesses previous mem accesses smp_mb() smp_mb() following mem accesses following mem accesses After the change, these pairs become: Thread A Thread B prev mem accesses prev mem accesses sys_membarrier() barrier() follow mem accesses follow mem accesses As we can see, there are two possible scenarios: either Thread B memory accesses do not happen concurrently with Thread A accesses (1), or they do (2). 1) Non-concurrent Thread A vs Thread B accesses: Thread A Thread B prev mem accesses sys_membarrier() follow mem accesses prev mem accesses barrier() follow mem accesses In this case, thread B accesses will be weakly ordered. This is OK, because at that point, thread A is not particularly interested in ordering them with respect to its own accesses. 2) Concurrent Thread A vs Thread B accesses Thread A Thread B prev mem accesses prev mem accesses sys_membarrier() barrier() follow mem accesses follow mem accesses In this case, thread B accesses, which are ensured to be in program order thanks to the compiler barrier, will be "upgraded" to full smp_mb() by synchronize_sched(). * Benchmarks On Intel Xeon E5405 (8 cores) (one thread is calling sys_membarrier, the other 7 threads are busy looping) 1000 non-expedited sys_membarrier calls in 33s =3D 33 milliseconds/call. * User-space user of this system call: Userspace RCU library Both the signal-based and the sys_membarrier userspace RCU schemes permit us to remove the memory barrier from the userspace RCU rcu_read_lock() and rcu_read_unlock() primitives, thus significantly accelerating them. These memory barriers are replaced by compiler barriers on the read-side, and all matching memory barriers on the write-side are turned into an invocation of a memory barrier on all active threads in the process. By letting the kernel perform this synchronization rather than dumbly sending a signal to every process threads (as we currently do), we diminish the number of unnecessary wake ups and only issue the memory barriers on active threads. Non-running threads do not need to execute such barrier anyway, because these are implied by the scheduler context switches. Results in liburcu: Operations in 10s, 6 readers, 2 writers: memory barriers in reader: 1701557485 reads, 2202847 writes signal-based scheme: 9830061167 reads, 6700 writes sys_membarrier: 9952759104 reads, 425 writes sys_membarrier (dyn. check): 7970328887 reads, 425 writes The dynamic sys_membarrier availability check adds some overhead to the read-side compared to the signal-based scheme, but besides that, sys_membarrier slightly outperforms the signal-based scheme. However, this non-expedited sys_membarrier implementation has a much slower grace period than signal and memory barrier schemes. Besides diminishing the number of wake-ups, one major advantage of the membarrier system call over the signal-based scheme is that it does not need to reserve a signal. This plays much more nicely with libraries, and with processes injected into for tracing purposes, for which we cannot expect that signals will be unused by the application. An expedited version of this system call can be added later on to speed up the grace period. Its implementation will likely depend on reading the cpu_curr()->mm without holding each CPU's rq lock. This patch adds the system call to x86 and to asm-generic. [1] http://urcu.so membarrier(2) man page: MEMBARRIER(2) Linux Programmer's Manual MEMBARRIER(2) NAME membarrier - issue memory barriers on a set of threads SYNOPSIS #include int membarrier(int cmd, int flags); DESCRIPTION The cmd argument is one of the following: MEMBARRIER_CMD_QUERY Query the set of supported commands. It returns a bitmask of supported commands. MEMBARRIER_CMD_SHARED Execute a memory barrier on all threads running on the system. Upon return from system call, the caller thread is ensured that all running threads have passed through a state where all memory accesses to user-space addresses match program order between entry to and return from the system call (non-running threads are de facto in such a state). This covers threads from all pro=E2=80=90 cesses running on the system. This command returns 0. The flags argument needs to be 0. For future extensions. All memory accesses performed in program order from each targeted thread is guaranteed to be ordered with respect to sys_membarrier(). If we use the semantic "barrier()" to represent a compiler barrier forcing memory accesses to be performed in program order across the barrier, and smp_mb() to represent explicit memory barriers forcing full memory ordering across the barrier, we have the following ordering table for each pair of barrier(), sys_membarrier() and smp_mb(): The pair ordering is detailed as (O: ordered, X: not ordered): barrier() smp_mb() sys_membarrier() barrier() X X O smp_mb() X O O sys_membarrier() O O O RETURN VALUE On success, these system calls return zero. On error, -1 is returned, and errno is set appropriately. For a given command, with flags argument set to 0, this system call is guaranteed to always return the same value until reboot. ERRORS ENOSYS System call is not implemented. EINVAL Invalid arguments. Linux 2015-04-15 MEMBARRIER(2) Signed-off-by: Mathieu Desnoyers Reviewed-by: Paul E. McKenney Reviewed-by: Josh Triplett Cc: KOSAKI Motohiro Cc: Steven Rostedt Cc: Nicholas Miell Cc: Ingo Molnar Cc: Alan Cox Cc: Lai Jiangshan Cc: Stephen Hemminger Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: David Howells Cc: Pranith Kumar Cc: Michael Kerrisk Cc: Shuah Khan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branches 'pm-cpu', 'pm-cpuidle' and 'pm-domains'

2015-09-11T13:37:36+00:00

* pm-cpu: kernel/cpu_pm: fix cpu_cluster_pm_exit comment * pm-cpuidle: cpuidle/coupled: Add sanity check for safe_state_index * pm-domains: staging: board: Migrate away from __pm_genpd_name_add_device() PM / Domains: Ensure subdomain is not in use before removing PM / Domains: Try power off masters in error path of __pm_genpd_poweron()

Merge branch 'akpm' (patches from Andrew)

2015-09-11T01:19:42+00:00

Merge third patch-bomb from Andrew Morton: - even more of the rest of MM - lib/ updates - checkpatch updates - small changes to a few scruffy filesystems - kmod fixes/cleanups - kexec updates - a dma-mapping cleanup series from hch * emailed patches from Andrew Morton : (81 commits) dma-mapping: consolidate dma_set_mask dma-mapping: consolidate dma_supported dma-mapping: cosolidate dma_mapping_error dma-mapping: consolidate dma_{alloc,free}_noncoherent dma-mapping: consolidate dma_{alloc,free}_{attrs,coherent} mm: use vma_is_anonymous() in create_huge_pmd() and wp_huge_pmd() mm: make sure all file VMAs have ->vm_ops set mm, mpx: add "vm_flags_t vm_flags" arg to do_mmap_pgoff() mm: mark most vm_operations_struct const namei: fix warning while make xmldocs caused by namei.c ipc: convert invalid scenarios to use WARN_ON zlib_deflate/deftree: remove bi_reverse() lib/decompress_unlzma: Do a NULL check for pointer lib/decompressors: use real out buf size for gunzip with kernel fs/affs: make root lookup from blkdev logical size sysctl: fix int -> unsigned long assignments in INT_MIN case kexec: export KERNEL_IMAGE_SIZE to vmcoreinfo kexec: align crash_notes allocation to make it be inside one physical page kexec: remove unnecessary test in kimage_alloc_crash_control_pages() kexec: split kexec_load syscall from kexec core code ...

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2015-09-10T20:53:15+00:00

Pull networking fixes from David Miller: 1) Fix out-of-bounds array access in netfilter ipset, from Jozsef Kadlecsik. 2) Use correct free operation on netfilter conntrack templates, from Daniel Borkmann. 3) Fix route leak in SCTP, from Marcelo Ricardo Leitner. 4) Fix sizeof(pointer) in mac80211, from Thierry Reding. 5) Fix cache pointer comparison in ip6mr leading to missed unlock of mrt_lock. From Richard Laing. 6) rds_conn_lookup() needs to consider network namespace in key comparison, from Sowmini Varadhan. 7) Fix deadlock in TIPC code wrt broadcast link wakeups, from Kolmakov Dmitriy. 8) Fix fd leaks in bpf syscall, from Daniel Borkmann. 9) Fix error recovery when installing ipv6 multipath routes, we would delete the old route before we would know if we could fully commit to the new set of nexthops. Fix from Roopa Prabhu. 10) Fix run-time suspend problems in r8152, from Hayes Wang. 11) In fec, don't program the MAC address into the chip when the clocks are gated off. From Fugang Duan. 12) Fix poll behavior for netlink sockets when using rx ring mmap, from Daniel Borkmann. 13) Don't allocate memory with GFP_KERNEL from get_stats64 in r8169 driver, from Corinna Vinschen. 14) In TCP Cubic congestion control, handle idle periods better where we are application limited, in order to keep cwnd from growing out of control. From Eric Dumzet. * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (65 commits) tcp_cubic: better follow cubic curve after idle period tcp: generate CA_EVENT_TX_START on data frames xen-netfront: respect user provided max_queues xen-netback: respect user provided max_queues r8169: Fix sleeping function called during get_stats64, v2 ether: add IEEE 1722 ethertype - TSN netlink, mmap: fix edge-case leakages in nf queue zero-copy netlink, mmap: don't walk rx ring on poll if receive queue non-empty cxgb4: changes for new firmware 1.14.4.0 net: fec: add netif status check before set mac address r8152: fix the runtime suspend issues r8152: split DRIVER_VERSION ipv6: fix ifnullfree.cocci warnings add microchip LAN88xx phy driver stmmac: fix check for phydev being open net: qlcnic: delete redundant memsets net: mv643xx_eth: use kzalloc net: jme: use kzalloc() instead of kmalloc+memset net: cavium: liquidio: use kzalloc in setup_glist() net: ipv6: use common fib_default_rule_pref ...

sysctl: fix int -> unsigned long assignments in INT_MIN case

2015-09-10T20:29:01+00:00

The following if (val < 0) *lvalp = (unsigned long)-val; is incorrect because the compiler is free to assume -val to be positive and use a sign-extend instruction for extending the bit pattern. This is a problem if val == INT_MIN: # echo -2147483648 >/proc/sys/dev/scsi/logging_level # cat /proc/sys/dev/scsi/logging_level -18446744071562067968 Cast to unsigned long before negation - that way we first sign-extend and then negate an unsigned, which is well defined. With this: # cat /proc/sys/dev/scsi/logging_level -2147483648 Signed-off-by: Ilya Dryomov Cc: Mikulas Patocka Cc: Robert Xiao Cc: "Eric W. Biederman" Cc: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kexec: export KERNEL_IMAGE_SIZE to vmcoreinfo

2015-09-10T20:29:01+00:00

In x86_64, since v2.6.26 the KERNEL_IMAGE_SIZE is changed to 512M, and accordingly the MODULES_VADDR is changed to 0xffffffffa0000000. However, in v3.12 Kees Cook introduced kaslr to randomise the location of kernel. And the kernel text mapping addr space is enlarged from 512M to 1G. That means now KERNEL_IMAGE_SIZE is variable, its value is 512M when kaslr support is not compiled in and 1G when kaslr support is compiled in. Accordingly the MODULES_VADDR is changed too to be: #define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE) So when kaslr is compiled in and enabled, the kernel text mapping addr space and modules vaddr space need be adjusted. Otherwise makedumpfile will collapse since the addr for some symbols is not correct. Hence KERNEL_IMAGE_SIZE need be exported to vmcoreinfo and got in makedumpfile to help calculate MODULES_VADDR. Signed-off-by: Baoquan He Acked-by: Kees Cook Acked-by: Vivek Goyal Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kexec: align crash_notes allocation to make it be inside one physical page

2015-09-10T20:29:01+00:00

People reported that crash_notes in /proc/vmcore were corrupted and this cause crash kdump failure. With code debugging and log we got the root cause. This is because percpu variable crash_notes are allocated in 2 vmalloc pages. Currently percpu is based on vmalloc by default. Vmalloc can't guarantee 2 continuous vmalloc pages are also on 2 continuous physical pages. So when 1st kernel exports the starting address and size of crash_notes through sysfs like below: /sys/devices/system/cpu/cpux/crash_notes /sys/devices/system/cpu/cpux/crash_notes_size kdump kernel use them to get the content of crash_notes. However the 2nd part may not be in the next neighbouring physical page as we expected if crash_notes are allocated accross 2 vmalloc pages. That's why nhdr_ptr->n_namesz or nhdr_ptr->n_descsz could be very huge in update_note_header_size_elf64() and cause note header merging failure or some warnings. In this patch change to call __alloc_percpu() to passed in the align value by rounding crash_notes_size up to the nearest power of two. This makes sure the crash_notes is allocated inside one physical page since sizeof(note_buf_t) in all ARCHS is smaller than PAGE_SIZE. Meanwhile add a BUILD_BUG_ON to break compile if size is bigger than PAGE_SIZE since crash_notes definitely will be in 2 pages. That need be avoided, and need be reported if it's unavoidable. [akpm@linux-foundation.org: use correct comment layout] Signed-off-by: Baoquan He Cc: Eric W. Biederman Cc: Vivek Goyal Cc: Dave Young Cc: Lisa Mitchell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kexec: remove unnecessary test in kimage_alloc_crash_control_pages()

2015-09-10T20:29:01+00:00

Transforming PFN(Page Frame Number) to struct page is never failure, so we can simplify the code logic to do the image->control_page assignment directly in the loop, and remove the unnecessary conditional judgement. Signed-off-by: Minfei Huang Acked-by: Dave Young Acked-by: Vivek Goyal Cc: Simon Horman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds