lwn.git/include/linux, branch doc/4.4

blk: rq_data_dir() should not return a boolean

2015-09-12T19:03:30+00:00

rq_data_dir() returns either READ or WRITE (0 == READ, 1 == WRITE), not a boolean value. Now, admittedly the "!= 0" doesn't really change the value (0 stays as zero, 1 stays as one), but it's not only redundant, it confuses gcc, and causes gcc to warn about the construct switch (rq_data_dir(req)) { case READ: ... case WRITE: ... that we have in a few drivers. Now, the gcc warning is silly and stupid (it seems to warn not about the switch value having a different type from the case statements, but about _any_ boolean switch value), but in this case the code itself is silly and stupid too, so let's just change it, and get rid of warnings like this: drivers/block/hd.c: In function ‘hd_request’: drivers/block/hd.c:630:11: warning: switch condition has boolean value [-Wswitch-bool] switch (rq_data_dir(req)) { The odd '!= 0' came in when "cmd_flags" got turned into a "u64" in commit 5953316dbf90 ("block: make rq->cmd_flags be 64-bit") and is presumably because the old code (that just did a logical 'and' with 1) would then end up making the type of rq_data_dir() be u64 too. But if we want to retain the old regular integer type, let's just cast the result to 'int' rather than use that rather odd '!= 0'. Signed-off-by: Linus Torvalds

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 'ntb-4.3' of git://github.com/jonmason/ntb

2015-09-12T02:29:00+00:00

Pull NTB fixes from Jon Mason: "NTB bug and documentation fixes, new device IDs, performance improvements, and adding a mailing list to MAINTAINERS for NTB" * tag 'ntb-4.3' of git://github.com/jonmason/ntb: NTB: Fix range check on memory window index NTB: Improve index handling in B2B MW workaround NTB: Fix documentation for ntb_peer_db_clear. NTB: Fix documentation for ntb_link_is_up NTB: Use unique DMA channels for TX and RX NTB: Remove dma_sync_wait from ntb_async_rx NTB: Clean up QP stats info NTB: Make the transport list in order of discovery NTB: Add PCI Device IDs for Broadwell Xeon NTB: Add flow control to the ntb_netdev NTB: Add list to MAINTAINERS

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

Merge tag 'media/v4.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media

2015-09-11T23:42:39+00:00

Pull media updates from Mauro Carvalho Chehab: "A series of patches that move part of the code used to allocate memory from the media subsystem to the mm subsystem" [ The mm parts have been acked by VM people, and the series was apparently in -mm for a while - Linus ] * tag 'media/v4.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: [media] drm/exynos: Convert g2d_userptr_get_dma_addr() to use get_vaddr_frames() [media] media: vb2: Remove unused functions [media] media: vb2: Convert vb2_dc_get_userptr() to use frame vector [media] media: vb2: Convert vb2_vmalloc_get_userptr() to use frame vector [media] media: vb2: Convert vb2_dma_sg_get_userptr() to use frame vector [media] vb2: Provide helpers for mapping virtual addresses [media] media: omap_vout: Convert omap_vout_uservirt_to_phys() to use get_vaddr_pfns() [media] mm: Provide new get_vaddr_frames() helper [media] vb2: Push mmap_sem down to memops

Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux

2015-09-11T23:13:47+00:00

Pull thermal updates from Zhang Rui: - use int instead of unsigned long to represent temperature to avoid bogus overheat detection when negative temperature reported. From Sascha Hauer. - export available thermal governors information to user space via sysfs. From Wei Ni. - introduce new thermal driver for Wildcat Point platform controller hub, which uses PCH thermal sensor and associated critical and hot trip points. From Tushar Dave. - add suuport for Intel Skylake and Denlow platforms in powerclamp driver. - some small cleanups in thermal core. * 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux: thermal: Add Intel PCH thermal driver thermal: Add comment explaining test for critical temperature thermal: Use IS_ENABLED instead of #ifdef thermal: remove unnecessary call to thermal_zone_device_set_polling thermal: trivial: fix typo in comment thermal: consistently use int for temperatures thermal: add available policies sysfs attribute thermal/powerclamp: add cpu id for denlow platform thermal/powerclamp: add cpu id for Skylake u/y thermal/powerclamp: add cpu id for skylake h/s

fs/seq_file: convert int seq_vprint/seq_printf/etc... returns to void

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

The seq_ function return values were frequently misused. See: commit 1f33c41c03da ("seq_file: Rename seq_overflow() to seq_has_overflowed() and make public") All uses of these return values have been removed, so convert the return types to void. Miscellanea: o Move seq_put_decimal_ and seq_escape prototypes closer the other seq_vprintf prototypes o Reorder seq_putc and seq_puts to return early on overflow o Add argument names to seq_vprintf and seq_printf o Update the seq_escape kernel-doc o Convert a couple of leading spaces to tabs in seq_escape Signed-off-by: Joe Perches Cc: Al Viro Cc: Steven Rostedt Cc: Mark Brown Cc: Stephen Rothwell Cc: Joerg Roedel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

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 branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client

2015-09-11T19:33:03+00:00

Pull Ceph update from Sage Weil: "There are a few fixes for snapshot behavior with CephFS and support for the new keepalive protocol from Zheng, a libceph fix that affects both RBD and CephFS, a few bug fixes and cleanups for RBD from Ilya, and several small fixes and cleanups from Jianpeng and others" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: ceph: improve readahead for file holes ceph: get inode size for each append write libceph: check data_len in ->alloc_msg() libceph: use keepalive2 to verify the mon session is alive rbd: plug rbd_dev->header.object_prefix memory leak rbd: fix double free on rbd_dev->header_name libceph: set 'exists' flag for newly up osd ceph: cleanup use of ceph_msg_get ceph: no need to get parent inode in ceph_open ceph: remove the useless judgement ceph: remove redundant test of head->safe and silence static analysis warnings ceph: fix queuing inode to mdsdir's snaprealm libceph: rename con_work() to ceph_con_workfn() libceph: Avoid holding the zero page on ceph_msgr_slab_init errors libceph: remove the unused macro AES_KEY_SIZE ceph: invalidate dirty pages after forced umount ceph: EIO all operations after forced umount

Merge branch 'pm-opp'

2015-09-11T13:37:17+00:00

* pm-opp: PM / OPP: Return suspend_opp only if it is enabled PM / OPP: add dev_pm_opp_get_suspend_opp() helper