user/sven/linux.git/kernel/locking, branch v4.19.17

locking/qspinlock, x86: Provide liveness guarantee

2018-12-21T13:15:12Z

commit 7aa54be2976550f17c11a1c3e3630002dea39303 upstream. On x86 we cannot do fetch_or() with a single instruction and thus end up using a cmpxchg loop, this reduces determinism. Replace the fetch_or() with a composite operation: tas-pending + load. Using two instructions of course opens a window we previously did not have. Consider the scenario: CPU0 CPU1 CPU2 1) lock trylock -> (0,0,1) 2) lock trylock /* fail */ 3) unlock -> (0,0,0) 4) lock trylock -> (0,0,1) 5) tas-pending -> (0,1,1) load-val <- (0,1,0) from 3 6) clear-pending-set-locked -> (0,0,1) FAIL: _2_ owners where 5) is our new composite operation. When we consider each part of the qspinlock state as a separate variable (as we can when _Q_PENDING_BITS == 8) then the above is entirely possible, because tas-pending will only RmW the pending byte, so the later load is able to observe prior tail and lock state (but not earlier than its own trylock, which operates on the whole word, due to coherence). To avoid this we need 2 things: - the load must come after the tas-pending (obviously, otherwise it can trivially observe prior state). - the tas-pending must be a full word RmW instruction, it cannot be an XCHGB for example, such that we cannot observe other state prior to setting pending. On x86 we can realize this by using "LOCK BTS m32, r32" for tas-pending followed by a regular load. Note that observing later state is not a problem: - if we fail to observe a later unlock, we'll simply spin-wait for that store to become visible. - if we observe a later xchg_tail(), there is no difference from that xchg_tail() having taken place before the tas-pending. Suggested-by: Will Deacon Reported-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Will Deacon Cc: Linus Torvalds Cc: Peter Zijlstra Cc: andrea.parri@amarulasolutions.com Cc: longman@redhat.com Fixes: 59fb586b4a07 ("locking/qspinlock: Remove unbounded cmpxchg() loop from locking slowpath") Link: https://lkml.kernel.org/r/20181003130957.183726335@infradead.org Signed-off-by: Ingo Molnar [bigeasy: GEN_BINARY_RMWcc macro redo] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Sasha Levin

locking/qspinlock: Re-order code

2018-12-21T13:15:11Z

commit 53bf57fab7321fb42b703056a4c80fc9d986d170 upstream. Flip the branch condition after atomic_fetch_or_acquire(_Q_PENDING_VAL) such that we loose the indent. This also result in a more natural code flow IMO. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: andrea.parri@amarulasolutions.com Cc: longman@redhat.com Link: https://lkml.kernel.org/r/20181003130257.156322446@infradead.org Signed-off-by: Ingo Molnar Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Sasha Levin

locking/lockdep: Fix debug_locks off performance problem

2018-11-13T19:08:20Z

[ Upstream commit 9506a7425b094d2f1d9c877ed5a78f416669269b ] It was found that when debug_locks was turned off because of a problem found by the lockdep code, the system performance could drop quite significantly when the lock_stat code was also configured into the kernel. For instance, parallel kernel build time on a 4-socket x86-64 server nearly doubled. Further analysis into the cause of the slowdown traced back to the frequent call to debug_locks_off() from the __lock_acquired() function probably due to some inconsistent lockdep states with debug_locks off. The debug_locks_off() function did an unconditional atomic xchg to write a 0 value into debug_locks which had already been set to 0. This led to severe cacheline contention in the cacheline that held debug_locks. As debug_locks is being referenced in quite a few different places in the kernel, this greatly slow down the system performance. To prevent that trashing of debug_locks cacheline, lock_acquired() and lock_contended() now checks the state of debug_locks before proceeding. The debug_locks_off() function is also modified to check debug_locks before calling __debug_locks_off(). Signed-off-by: Waiman Long Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Link: http://lkml.kernel.org/r/1539913518-15598-1-git-send-email-longman@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

locking/ww_mutex: Fix runtime warning in the WW mutex selftest

2018-10-03T06:56:31Z

If CONFIG_WW_MUTEX_SELFTEST=y is enabled, booting an image in an arm64 virtual machine results in the following traceback if 8 CPUs are enabled: DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current) WARNING: CPU: 2 PID: 537 at kernel/locking/mutex.c:1033 __mutex_unlock_slowpath+0x1a8/0x2e0 ... Call trace: __mutex_unlock_slowpath() ww_mutex_unlock() test_cycle_work() process_one_work() worker_thread() kthread() ret_from_fork() If requesting b_mutex fails with -EDEADLK, the error variable is reassigned to the return value from calling ww_mutex_lock on a_mutex again. If this call fails, a_mutex is not locked. It is, however, unconditionally unlocked subsequently, causing the reported warning. Fix the problem by using two error variables. With this change, the selftest still fails as follows: cyclic deadlock not resolved, ret[7/8] = -35 However, the traceback is gone. Signed-off-by: Guenter Roeck Cc: Chris Wilson Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Fixes: d1b42b800e5d0 ("locking/ww_mutex: Add kselftests for resolving ww_mutex cyclic deadlocks") Link: http://lkml.kernel.org/r/1538516929-9734-1-git-send-email-linux@roeck-us.net Signed-off-by: Ingo Molnar

locking/ww_mutex: Fix spelling mistake "cylic" -> "cyclic"

2018-09-10T12:00:01Z

Trivial fix to spelling mistake in pr_err() error message Signed-off-by: Colin Ian King Acked-by: Will Deacon Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: kernel-janitors@vger.kernel.org Link: http://lkml.kernel.org/r/20180824112235.8842-1-colin.king@canonical.com Signed-off-by: Ingo Molnar

locking/lockdep: Delete unnecessary #include

2018-09-10T11:48:25Z

Commit: c3bc8fd637a9 ("tracing: Centralize preemptirq tracepoints and unify their usage") added the inclusion of . liblockdep doesn't have a stub version of that header so now fails to build. However, commit: bff1b208a5d1 ("tracing: Partial revert of "tracing: Centralize preemptirq tracepoints and unify their usage"") removed the use of functions declared in that header. So delete the #include. Signed-off-by: Ben Hutchings Cc: Joel Fernandes Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Sasha Levin Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Will Deacon Fixes: bff1b208a5d1 ("tracing: Partial revert of "tracing: Centralize ...") Fixes: c3bc8fd637a9 ("tracing: Centralize preemptirq tracepoints ...") Link: http://lkml.kernel.org/r/20180828203315.GD18030@decadent.org.uk Signed-off-by: Ingo Molnar

locking/mutex: Fix mutex debug call and ww_mutex documentation

2018-09-10T08:05:10Z

The following commit: 08295b3b5bee ("Implement an algorithm choice for Wound-Wait mutexes") introduced a reference in the documentation to a function that was removed in an earlier commit. It also forgot to remove a call to debug_mutex_add_waiter() which is now unconditionally called by __mutex_add_waiter(). Fix those bugs. Signed-off-by: Thomas Hellstrom Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dri-devel@lists.freedesktop.org Fixes: 08295b3b5bee ("Implement an algorithm choice for Wound-Wait mutexes") Link: http://lkml.kernel.org/r/20180903140708.2401-1-thellstrom@vmware.com Signed-off-by: Ingo Molnar

Merge tag 'trace-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2018-08-21T01:32:00Z

Pull tracing updates from Steven Rostedt: - Restructure of lockdep and latency tracers This is the biggest change. Joel Fernandes restructured the hooks from irqs and preemption disabling and enabling. He got rid of a lot of the preprocessor #ifdef mess that they caused. He turned both lockdep and the latency tracers to use trace events inserted in the preempt/irqs disabling paths. But unfortunately, these started to cause issues in corner cases. Thus, parts of the code was reverted back to where lockdep and the latency tracers just get called directly (without using the trace events). But because the original change cleaned up the code very nicely we kept that, as well as the trace events for preempt and irqs disabling, but they are limited to not being called in NMIs. - Have trace events use SRCU for "rcu idle" calls. This was required for the preempt/irqs off trace events. But it also had to not allow them to be called in NMI context. Waiting till Paul makes an NMI safe SRCU API. - New notrace SRCU API to allow trace events to use SRCU. - Addition of mcount-nop option support - SPDX headers replacing GPL templates. - Various other fixes and clean ups. - Some fixes are marked for stable, but were not fully tested before the merge window opened. * tag 'trace-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (44 commits) tracing: Fix SPDX format headers to use C++ style comments tracing: Add SPDX License format tags to tracing files tracing: Add SPDX License format to bpf_trace.c blktrace: Add SPDX License format header s390/ftrace: Add -mfentry and -mnop-mcount support tracing: Add -mcount-nop option support tracing: Avoid calling cc-option -mrecord-mcount for every Makefile tracing: Handle CC_FLAGS_FTRACE more accurately Uprobe: Additional argument arch_uprobe to uprobe_write_opcode() Uprobes: Simplify uprobe_register() body tracepoints: Free early tracepoints after RCU is initialized uprobes: Use synchronize_rcu() not synchronize_sched() tracing: Fix synchronizing to event changes with tracepoint_synchronize_unregister() ftrace: Remove unused pointer ftrace_swapper_pid tracing: More reverting of "tracing: Centralize preemptirq tracepoints and unify their usage" tracing/irqsoff: Handle preempt_count for different configs tracing: Partial revert of "tracing: Centralize preemptirq tracepoints and unify their usage" tracing: irqsoff: Account for additional preempt_disable trace: Use rcu_dereference_raw for hooks from trace-event subsystem tracing/kprobes: Fix within_notrace_func() to check only notrace functions ...

Merge tag 'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm

2018-08-16T00:39:07Z

Pull drm updates from Dave Airlie: "This is the main drm pull request for 4.19. Rob has some new hardware support for new qualcomm hw that I'll send along separately. This has the display part of it, the remaining pull is for the acceleration engine. This also contains a wound-wait/wait-die mutex rework, Peter has acked it for merging via my tree. Otherwise mostly the usual level of activity. Summary: core: - Wound-wait/wait-die mutex rework - Add writeback connector type - Add "content type" property for HDMI - Move GEM bo to drm_framebuffer - Initial gpu scheduler documentation - GPU scheduler fixes for dying processes - Console deferred fbcon takeover support - Displayport support for CEC tunneling over AUX panel: - otm8009a panel driver fixes - Innolux TV123WAM and G070Y2-L01 panel driver - Ilitek ILI9881c panel driver - Rocktech RK070ER9427 LCD - EDT ETM0700G0EDH6 and EDT ETM0700G0BDH6 - DLC DLC0700YZG-1 - BOE HV070WSA-100 - newhaven, nhd-4.3-480272ef-atxl LCD - DataImage SCF0700C48GGU18 - Sharp LQ035Q7DB03 - p079zca: Refactor to support multiple panels tinydrm: - ILI9341 display panel New driver: - vkms - virtual kms driver to testing. i915: - Icelake: Display enablement DSI support IRQ support Powerwell support - GPU reset fixes and improvements - Full ppgtt support refactoring - PSR fixes and improvements - Execlist improvments - GuC related fixes amdgpu: - Initial amdgpu documentation - JPEG engine support on VCN - CIK uses powerplay by default - Move to using core PCIE functionality for gens/lanes - DC/Powerplay interface rework - Stutter mode support for RV - Vega12 Powerplay updates - GFXOFF fixes - GPUVM fault debugging - Vega12 GFXOFF - DC improvements - DC i2c/aux changes - UVD 7.2 fixes - Powerplay fixes for Polaris12, CZ/ST - command submission bo_list fixes amdkfd: - Raven support - Power management fixes udl: - Cleanups and fixes nouveau: - misc fixes and cleanups. msm: - DPU1 support display controller in sdm845 - GPU coredump support. vmwgfx: - Atomic modesetting validation fixes - Support for multisample surfaces armada: - Atomic modesetting support completed. exynos: - IPPv2 fixes - Move g2d to component framework - Suspend/resume support cleanups - Driver cleanups imx: - CSI configuration improvements - Driver cleanups - Use atomic suspend/resume helpers - ipu-v3 V4L2 XRGB32/XBGR32 support pl111: - Add Nomadik LCDC variant v3d: - GPU scheduler jobs management sun4i: - R40 display engine support - TCON TOP driver mediatek: - MT2712 SoC support rockchip: - vop fixes omapdrm: - Workaround for DRA7 errata i932 - Fix mm_list locking mali-dp: - Writeback implementation PM improvements - Internal error reporting debugfs tilcdc: - Single fix for deferred probing hdlcd: - Teardown fixes tda998x: - Converted to a bridge driver. etnaviv: - Misc fixes" * tag 'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm: (1506 commits) drm/amdgpu/sriov: give 8s for recover vram under RUNTIME drm/scheduler: fix param documentation drm/i2c: tda998x: correct PLL divider calculation drm/i2c: tda998x: get rid of private fill_modes function drm/i2c: tda998x: move mode_valid() to bridge drm/i2c: tda998x: register bridge outside of component helper drm/i2c: tda998x: cleanup from previous changes drm/i2c: tda998x: allocate tda998x_priv inside tda998x_create() drm/i2c: tda998x: convert to bridge driver drm/scheduler: fix timeout worker setup for out of order job completions drm/amd/display: display connected to dp-1 does not light up drm/amd/display: update clk for various HDMI color depths drm/amd/display: program display clock on cache match drm/amd/display: Add NULL check for enabling dp ss drm/amd/display: add vbios table check for enabling dp ss drm/amd/display: Don't share clk source between DP and HDMI drm/amd/display: Fix DP HBR2 Eye Diagram Pattern on Carrizo drm/amd/display: Use calculated disp_clk_khz value for dce110 drm/amd/display: Implement custom degamma lut on dcn drm/amd/display: Destroy aux_engines only once ...

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2018-08-13T17:49:41Z

Pull RCU updates from Thomas Gleixner: "A large update to RCU: Preparatory work for consolidating the RCU flavors: - Introduce grace-period sequence numbers to the RCU-bh, RCU-preempt, and RCU-sched flavors, replacing the old ->gpnum and ->completed pair of fields. This change allows lockless code to obtain the complete grace-period state with a single READ_ONCE(), which is needed to maintain tolerable lock contention during the upcoming consolidation of the three RCU flavors. Note that grace-period sequence numbers are already used by rcu_barrier(), expedited RCU grace periods, and SRCU, and are thus already heavily used and well-tested. Joel Fernandes contributed a number of excellent fixes and improvements. - Clean up some grace-period-reporting loose ends, including improving the handling of quiescent states from offline CPUs and fixing some false-positive WARN_ON_ONCE() invocations. (Strictly speaking, the WARN_ON_ONCE() invocations were quite correct, but their invariants were (harmlessly) violated by the earlier sloppy handling of quiescent states from offline CPUs.) In addition, improve grace-period forward-progress guarantees so as to allow removal of fail-safe checks that required otherwise needless lock acquisitions. Finally, add more diagnostics to help debug the upcoming consolidation of the RCU-bh, RCU-preempt, and RCU-sched flavors. The rest: - SRCU updates - Updates to rcutorture and associated scripting. - The usual pile of miscellaneous fixes" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (118 commits) rcutorture: Fix rcu_barrier successes counter rcutorture: Add support to detect if boost kthread prio is too low rcutorture: Use monotonic timestamp for stall detection rcutorture: Make boost test more robust rcutorture: Disable RT throttling for boost tests rcutorture: Emphasize testing of single reader protection type rcutorture: Handle extended read-side critical sections rcutorture: Make rcu_torture_timer() use rcu_torture_one_read() rcutorture: Use per-CPU random state for rcu_torture_timer() rcutorture: Use atomic increment for n_rcu_torture_timers rcutorture: Extract common code from rcu_torture_reader() rcuperf: Remove unused torturing_tasks() function rcu: Remove rcutorture test version and sequence number rcutorture: Change units of onoff_interval to jiffies rcu: Assign higher prio to RCU threads if rcutorture is built-in rculist: Improve documentation for list_for_each_entry_from_rcu() srcu: Add grace-period number to rcutorture statistics printout rcu: Print stall-warning NMI dyntick state in hexadecimal MAINTAINERS: Update RCU, SRCU, and TORTURE-TEST entries rcu: Make rcu_seq_diff() more exact ...