The current code provokes some kernel-doc warnings:

	./kernel/rcu/tree.c:2915: warning: Function parameter or member 'count' not described in 'kfree_rcu_cpu'
	./include/linux/rculist.h:517: warning: bad line:                           [@right ][node2 ... ]
	./include/linux/rculist.h:2: WARNING: Unexpected indentation.

This commit therefore moves the comment for "count" to the kernel-doc
markup and adds a missing "*" on one kernel-doc continuation line.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Fix kernel-doc warning:

../kernel/rcu/tree.c:959: warning: Excess function parameter 'irq' description in 'rcu_nmi_enter'

Fixes: cf7614e1 ("rcu: Refactor rcu_{nmi,irq}_{enter,exit}()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The ->grpnum field in the rcu_node structure contains the bit position
in this structure's parent's bitmasks, which is not the CPU number.
This commit therefore adjusts this field's comment accordingly.
Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The ->grplo and ->grphi fields store the lowest and highest CPU number
covered by to a rcu_node structure, which is not the group number.
This commit therefore adjusts these fields' comments to match reality.
Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Because gp_max is protected by root rcu_node's lock, this commit moves
the gp_max definition to the region of the rcu_node structure containing
fields protected by this lock.
Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The count and scan can be separated in time, and there is a fair chance
that all work is already done when the scan starts, which might in turn
result in a needless retry.  This commit therefore avoids this retry by
returning SHRINK_STOP.
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Peter Enderborg <peter.enderborg@sony.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Coccinelle reports a warning

WARNING: Assignment of 0/1 to bool variable

The root cause is that the variable lastphase is a bool, but is
initialised with integer 1.  This commit therefore replaces the 1 with
a true.
Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Currently, lockdep_rcu_suspicious() complains twice about RCU read-side
critical sections being invoked from within extended quiescent states,
for example:

	RCU used illegally from idle CPU!
	rcu_scheduler_active = 2, debug_locks = 1
	RCU used illegally from extended quiescent state!

This commit therefore saves a couple lines of code and one line of
console-log output by eliminating the first of these two complaints.

Link: https://lore.kernel.org/lkml/87wo4wnpzb.fsf@nanos.tec.linutronix.de
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The objtool complains about the call to rcu_cleanup_after_idle() from
rcu_nmi_enter(), so this commit adds instrumentation_begin() before that
call and instrumentation_end() after it.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit removes the variable rnp from check_slow_task(), which
is defined, assigned to, but not otherwise used.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Setting a tick dependency on any task, including the case where a task
sets that dependency on itself, triggers an IPI to all CPUs.  That is
of course suboptimal but it had previously not been an issue because it
was only used by POSIX CPU timers on nohz_full, which apparently never
occurs in latency-sensitive workloads in production.  (Or users of such
systems are suffering in silence on the one hand or venting their ire
on the wrong people on the other.)

But RCU now sets a task tick dependency on the current task in order
to fix stall issues that can occur during RCU callback processing.
Thus, RCU callback processing triggers frequent system-wide IPIs from
nohz_full CPUs.  This is quite counter-productive, after all, avoiding
IPIs is what nohz_full is supposed to be all about.

This commit therefore optimizes tasks' self-setting of a task tick
dependency by using tick_nohz_full_kick() to avoid the system-wide IPI.
Instead, only the execution of the one task is disturbed, which is
acceptable given that this disturbance is well down into the noise
compared to the degree to which the RCU callback processing itself
disturbs execution.

Fixes: 6a949b7a (rcu: Force on tick when invoking lots of callbacks)
Reported-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@kernel.org
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Signed-off-by: Lihao Liang <lihaoliang@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Very large I/Os can cause the following RCU CPU stall warning:

RIP: 0010:rb_prev+0x8/0x50
Code: 49 89 c0 49 89 d1 48 89 c2 48 89 f8 e9 e5 fd ff ff 4c 89 48 10 c3 4c =
89 06 c3 4c 89 40 10 c3 0f 1f 00 48 8b 0f 48 39 cf 74 38 <48> 8b 47 10 48 85 c0 74 22 48 8b 50 08 48 85 d2 74 0c 48 89 d0 48
RSP: 0018:ffffc9002212bab0 EFLAGS: 00000287 ORIG_RAX: ffffffffffffff13
RAX: ffff888821f93630 RBX: ffff888821f93630 RCX: ffff888821f937e0
RDX: 0000000000000000 RSI: 0000000000102000 RDI: ffff888821f93630
RBP: 0000000000103000 R08: 000000000006c000 R09: 0000000000000238
R10: 0000000000102fff R11: ffffc9002212bac8 R12: 0000000000000001
R13: ffffffffffffffff R14: 0000000000102000 R15: ffff888821f937e0
 __lookup_extent_mapping+0xa0/0x110
 try_release_extent_mapping+0xdc/0x220
 btrfs_releasepage+0x45/0x70
 shrink_page_list+0xa39/0xb30
 shrink_inactive_list+0x18f/0x3b0
 shrink_lruvec+0x38e/0x6b0
 shrink_node+0x14d/0x690
 do_try_to_free_pages+0xc6/0x3e0
 try_to_free_mem_cgroup_pages+0xe6/0x1e0
 reclaim_high.constprop.73+0x87/0xc0
 mem_cgroup_handle_over_high+0x66/0x150
 exit_to_usermode_loop+0x82/0xd0
 do_syscall_64+0xd4/0x100
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

On a PREEMPT=n kernel, the try_release_extent_mapping() function's
"while" loop might run for a very long time on a large I/O.  This commit
therefore adds a cond_resched() to this loop, providing RCU any needed
quiescent states.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit converts the schedule_timeout_uninterruptible() call used
by RCU's expedited grace-period processing to schedule_timeout_idle().
This conversion avoids polluting the load-average with RCU-related
sleeping.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit converts the schedule_timeout_interruptible() call used by
RCU's no-CBs grace-period kthreads to schedule_timeout_idle().  This
conversion avoids polluting the load-average with RCU-related sleeping.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit converts the long-standing schedule_timeout_interruptible()
call used by RCU's priority-boosting kthreads to schedule_timeout_idle().
This conversion avoids polluting the load-average with RCU-related
sleeping.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit converts the long-standing schedule_timeout_interruptible()
and schedule_timeout_uninterruptible() calls used by RCU's grace-period
kthread to schedule_timeout_idle().  This conversion avoids polluting
the load-average with RCU-related sleeping.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The different strings used for describing the polarity are
Start, End and StillNonIdle. Since StillIdle is not used in any trace
point for rcu_dyntick, it can be removed and StillNonIdle can be added
in the description. Because StillNonIdle is used in a few tracepoints for
rcu_dyntick.

Similarly, USER, IDLE and IRQ are used for describing context in
the rcu_dyntick tracepoints. Since, "KERNEL" is not used for any
of the rcu_dyntick tracepoints, remove it from the description.
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The rcu_callback_map lockdep_map structure was added back in 2013, but
its purpose has become obscure.  This commit therefore documments that the
purpose of rcu_callback map is, in the words of commit 24ef659a ("rcu:
Provide better diagnostics for blocking in RCU callback functions"),
to help lockdep to tie an "inappropriate voluntary context switch back
to the fact that the function is being invoked from within a callback."
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit adds a count of the callbacks invoked to the per-CPU rcu_data
structure.  This count is printed by the show_rcu_gp_kthreads() that
is invoked by rcutorture and the RCU CPU stall-warning code.  It is also
intended for use by drgn.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

There is only 1 bit set in mask, which means that the only difference
between oldmask and the new one will be at the position where the bit is
set in mask.  This commit therefore updates rcu_state.ncpus by checking
whether the bit in mask is already set in rnp->expmaskinitnext.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

A large process running on a heavily loaded system can encounter the
following RCU CPU stall warning:

  rcu: INFO: rcu_sched self-detected stall on CPU
  rcu: 	3-....: (20998 ticks this GP) idle=4ea/1/0x4000000000000002 softirq=556558/556558 fqs=5190
  	(t=21013 jiffies g=1005461 q=132576)
  NMI backtrace for cpu 3
  CPU: 3 PID: 501900 Comm: aio-free-ring-w Kdump: loaded Not tainted 5.2.9-108_fbk12_rc3_3858_gb83b75af7909 #1
  Hardware name: Wiwynn   HoneyBadger/PantherPlus, BIOS HBM6.71 02/03/2016
  Call Trace:
   <IRQ>
   dump_stack+0x46/0x60
   nmi_cpu_backtrace.cold.3+0x13/0x50
   ? lapic_can_unplug_cpu.cold.27+0x34/0x34
   nmi_trigger_cpumask_backtrace+0xba/0xca
   rcu_dump_cpu_stacks+0x99/0xc7
   rcu_sched_clock_irq.cold.87+0x1aa/0x397
   ? tick_sched_do_timer+0x60/0x60
   update_process_times+0x28/0x60
   tick_sched_timer+0x37/0x70
   __hrtimer_run_queues+0xfe/0x270
   hrtimer_interrupt+0xf4/0x210
   smp_apic_timer_interrupt+0x5e/0x120
   apic_timer_interrupt+0xf/0x20
   </IRQ>
  RIP: 0010:kmem_cache_free+0x223/0x300
  Code: 88 00 00 00 0f 85 ca 00 00 00 41 8b 55 18 31 f6 f7 da 41 f6 45 0a 02 40 0f 94 c6 83 c6 05 9c 41 5e fa e8 a0 a7 01 00 41 56 9d <49> 8b 47 08 a8 03 0f 85 87 00 00 00 65 48 ff 08 e9 3d fe ff ff 65
  RSP: 0018:ffffc9000e8e3da8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
  RAX: 0000000000020000 RBX: ffff88861b9de960 RCX: 0000000000000030
  RDX: fffffffffffe41e8 RSI: 000060777fe3a100 RDI: 000000000001be18
  RBP: ffffea00186e7780 R08: ffffffffffffffff R09: ffffffffffffffff
  R10: ffff88861b9dea28 R11: ffff88887ffde000 R12: ffffffff81230a1f
  R13: ffff888854684dc0 R14: 0000000000000206 R15: ffff8888547dbc00
   ? remove_vma+0x4f/0x60
   remove_vma+0x4f/0x60
   exit_mmap+0xd6/0x160
   mmput+0x4a/0x110
   do_exit+0x278/0xae0
   ? syscall_trace_enter+0x1d3/0x2b0
   ? handle_mm_fault+0xaa/0x1c0
   do_group_exit+0x3a/0xa0
   __x64_sys_exit_group+0x14/0x20
   do_syscall_64+0x42/0x100
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

And on a PREEMPT=n kernel, the "while (vma)" loop in exit_mmap() can run
for a very long time given a large process.  This commit therefore adds
a cond_resched() to this loop, providing RCU any needed quiescent states.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-mm@kvack.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The __wait_rcu_gp() function unconditionally initializes and cleans up
each element of rs_array[], whether used or not.  This is slightly
wasteful and rather confusing, so this commit skips both initialization
and cleanup for duplicate callback functions.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Pull ARM OMAP fixes from Arnd Bergmann:
 "The OMAP developers are particularly active at hunting down
  regressions, so this is a separate branch with OMAP specific
  fixes for v5.8:

  As Tony explains
    "The recent display subsystem (DSS) related platform data changes
     caused display related regressions for suspend and resume. Looks
     like I only tested suspend and resume before dropping the legacy
     platform data, and forgot to test it after dropping it. Turns out
     the main issue was that we no longer have platform code calling
     pm_runtime_suspend for DSS like we did for the legacy platform data
     case, and that fix is still being discussed on the dri-devel list
     and will get merged separately. The DSS related testing exposed a
     pile other other display related issues that also need fixing
     though":

   - Fix ti-sysc optional clock handling and reset status checks for
     devices that reset automatically in idle like DSS

   - Ignore ti-sysc clockactivity bit unless separately requested to
     avoid unexpected performance issues

   - Init ti-sysc framedonetv_irq to true and disable for am4

   - Avoid duplicate DSS reset for legacy mode with dts data

   - Remove LCD timings for am4 as they cause warnings now that we're
     using generic panels

  Other OMAP changes from Tony include:

   - Fix omap_prm reset deassert as we still have drivers setting the
     pm_runtime_irq_safe() flag

   - Flush posted write for ti-sysc enable and disable

   - Fix droid4 spi related errors with spi flags

   - Fix am335x USB range and a typo for softreset

   - Fix dra7 timer nodes for clocks for IPU and DSP

   - Drop duplicate mailboxes after mismerge for dra7

   - Prevent pocketgeagle header line signal from accidentally setting
     micro-SD write protection signal by removing the default mux

   - Fix NFSroot flakeyness after resume for duover by switching the
     smsc911x gpio interrupt to back to level sensitive

   - Fix regression for omap4 clockevent source after recent system
     timer changes

   - Yet another ethernet regression fix for the "rgmii" vs "rgmii-rxid"
     phy-mode

   - One patch to convert am3/am4 DT files to use the regular sdhci-omap
     driver instead of the old hsmmc driver, this was meant for the
     merge window but got lost in the process"

* tag 'arm-omap-fixes-5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (21 commits)
  ARM: dts: am5729: beaglebone-ai: fix rgmii phy-mode
  ARM: dts: Fix omap4 system timer source clocks
  ARM: dts: Fix duovero smsc interrupt for suspend
  ARM: dts: am335x-pocketbeagle: Fix mmc0 Write Protect
  Revert "bus: ti-sysc: Increase max softreset wait"
  ARM: dts: am437x-epos-evm: remove lcd timings
  ARM: dts: am437x-gp-evm: remove lcd timings
  ARM: dts: am437x-sk-evm: remove lcd timings
  ARM: dts: dra7-evm-common: Fix duplicate mailbox nodes
  ARM: dts: dra7: Fix timer nodes properly for timer_sys_ck clocks
  ARM: dts: Fix am33xx.dtsi ti,sysc-mask wrong softreset flag
  ARM: dts: Fix am33xx.dtsi USB ranges length
  bus: ti-sysc: Increase max softreset wait
  ARM: OMAP2+: Fix legacy mode dss_reset
  bus: ti-sysc: Fix uninitialized framedonetv_irq
  bus: ti-sysc: Ignore clockactivity unless specified as a quirk
  bus: ti-sysc: Use optional clocks on for enable and wait for softreset bit
  ARM: dts: omap4-droid4: Fix spi configuration and increase rate
  bus: ti-sysc: Flush posted write on enable and disable
  soc: ti: omap-prm: use atomic iopoll instead of sleeping one
  ...

Pull ARM SoC fixes from Arnd Bergmann:
 "Here are a couple of bug fixes, mostly for devicetree files

  NXP i.MX:
   - Use correct voltage on some i.MX8M board device trees to avoid
     hardware damage
   - Code fixes for a compiler warning and incorrect reference counting,
     both harmless.
   - Fix the i.MX8M SoC driver to correctly identify imx8mp
   - Fix watchdog configuration in imx6ul-kontron device tree.

  Broadcom:
   - A small regression fix for the Raspberry-Pi firmware driver
   - A Kconfig change to use the correct timer driver on Northstar
   - A DT fix for the Luxul XWC-2000 machine
   - Two more DT fixes for NSP SoCs

  STmicroelectronics STI
   - Revert one broken patch for L2 cache configuration

  ARM Versatile Express:
   - Fix a regression by reverting a broken DT cleanup

  TEE drivers:
   - MAINTAINERS: change tee mailing list"

* tag 'arm-fixes-5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc:
  Revert "ARM: sti: Implement dummy L2 cache's write_sec"
  soc: imx8m: fix build warning
  ARM: imx6: add missing put_device() call in imx6q_suspend_init()
  ARM: imx5: add missing put_device() call in imx_suspend_alloc_ocram()
  soc: imx8m: Correct i.MX8MP UID fuse offset
  ARM: dts: imx6ul-kontron: Change WDOG_ANY signal from push-pull to open-drain
  ARM: dts: imx6ul-kontron: Move watchdog from Kontron i.MX6UL/ULL board to SoM
  arm64: dts: imx8mm-beacon: Fix voltages on LDO1 and LDO2
  arm64: dts: imx8mn-ddr4-evk: correct ldo1/ldo2 voltage range
  arm64: dts: imx8mm-evk: correct ldo1/ldo2 voltage range
  ARM: dts: NSP: Correct FA2 mailbox node
  ARM: bcm2835: Fix integer overflow in rpi_firmware_print_firmware_revision()
  MAINTAINERS: change tee mailing list
  ARM: dts: NSP: Disable PL330 by default, add dma-coherent property
  ARM: bcm: Select ARM_TIMER_SP804 for ARCH_BCM_NSP
  ARM: dts: BCM5301X: Add missing memory "device_type" for Luxul XWC-2000
  arm: dts: vexpress: Move mcc node back into motherboard node

Pull timer fix from Ingo Molnar:
 "A single DocBook fix"

* tag 'timers-urgent-2020-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timekeeping: Fix kerneldoc system_device_crosststamp & al

Pull perf fix from Ingo Molnar:
 "A single Kbuild dependency fix"

* tag 'perf-urgent-2020-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/rapl: Fix RAPL config variable bug

Pull EFI fixes from Ingo Molnar:

 - Fix build regression on v4.8 and older

 - Robustness fix for TPM log parsing code

 - kobject refcount fix for the ESRT parsing code

 - Two efivarfs fixes to make it behave more like an ordinary file
   system

 - Style fixup for zero length arrays

 - Fix a regression in path separator handling in the initrd loader

 - Fix a missing prototype warning

 - Add some kerneldoc headers for newly introduced stub routines

 - Allow support for SSDT overrides via EFI variables to be disabled

 - Report CPU mode and MMU state upon entry for 32-bit ARM

 - Use the correct stack pointer alignment when entering from mixed mode

* tag 'efi-urgent-2020-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efi/libstub: arm: Print CPU boot mode and MMU state at boot
  efi/libstub: arm: Omit arch specific config table matching array on arm64
  efi/x86: Setup stack correctly for efi_pe_entry
  efi: Make it possible to disable efivar_ssdt entirely
  efi/libstub: Descriptions for stub helper functions
  efi/libstub: Fix path separator regression
  efi/libstub: Fix missing-prototype warning for skip_spaces()
  efi: Replace zero-length array and use struct_size() helper
  efivarfs: Don't return -EINTR when rate-limiting reads
  efivarfs: Update inode modification time for successful writes
  efi/esrt: Fix reference count leak in esre_create_sysfs_entry.
  efi/tpm: Verify event log header before parsing
  efi/x86: Fix build with gcc 4

Pull scheduler fixes from Borislav Petkov:
 "The most anticipated fix in this pull request is probably the horrible
  build fix for the RANDSTRUCT fail that didn't make -rc2. Also included
  is the cleanup that removes those BUILD_BUG_ON()s and replaces it with
  ugly unions.

  Also included is the try_to_wake_up() race fix that was first
  triggered by Paul's RCU-torture runs, but was independently hit by
  Dave Chinner's fstest runs as well"

* tag 'sched_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cfs: change initial value of runnable_avg
  smp, irq_work: Continue smp_call_function*() and irq_work*() integration
  sched/core: s/WF_ON_RQ/WQ_ON_CPU/
  sched/core: Fix ttwu() race
  sched/core: Fix PI boosting between RT and DEADLINE tasks
  sched/deadline: Initialize ->dl_boosted
  sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption
  sched/core: Fix CONFIG_GCC_PLUGIN_RANDSTRUCT build fail

Pull x86 fixes from Borislav Petkov:

 - AMD Memory bandwidth counter width fix, by Babu Moger.

 - Use the proper length type in the 32-bit truncate() syscall variant,
   by Jiri Slaby.

 - Reinit IA32_FEAT_CTL during wakeup to fix the case where after
   resume, VMXON would #GP due to VMX not being properly enabled, by
   Sean Christopherson.

 - Fix a static checker warning in the resctrl code, by Dan Carpenter.

 - Add a CR4 pinning mask for bits which cannot change after boot, by
   Kees Cook.

 - Align the start of the loop of __clear_user() to 16 bytes, to improve
   performance on AMD zen1 and zen2 microarchitectures, by Matt Fleming.

* tag 'x86_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm/64: Align start of __clear_user() loop to 16-bytes
  x86/cpu: Use pinning mask for CR4 bits needing to be 0
  x86/resctrl: Fix a NULL vs IS_ERR() static checker warning in rdt_cdp_peer_get()
  x86/cpu: Reinitialize IA32_FEAT_CTL MSR on BSP during wakeup
  syscalls: Fix offset type of ksys_ftruncate()
  x86/resctrl: Fix memory bandwidth counter width for AMD

Pull RCU-vs-KCSAN fixes from Borislav Petkov:
 "A single commit that uses "arch_" atomic operations to avoid the
  instrumentation that comes with the non-"arch_" versions.

  In preparation for that commit, it also has another commit that makes
  these "arch_" atomic operations available to generic code.

  Without these commits, KCSAN uses can see pointless errors"

* tag 'rcu_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Fixup noinstr warnings
  locking/atomics: Provide the arch_atomic_ interface to generic code

Pull objtool fixes from Borislav Petkov:
 "Three fixes from Peter Zijlstra suppressing KCOV instrumentation in
  noinstr sections.

  Peter Zijlstra says:
    "Address KCOV vs noinstr. There is no function attribute to
     selectively suppress KCOV instrumentation, instead teach objtool
     to NOP out the calls in noinstr functions"

  This cures a bunch of KCOV crashes (as used by syzcaller)"

* tag 'objtool_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Fix noinstr vs KCOV
  objtool: Provide elf_write_{insn,reloc}()
  objtool: Clean up elf_write() condition

Pull x86 entry fixes from Borislav Petkov:
 "This is the x86/entry urgent pile which has accumulated since the
  merge window.

  It is not the smallest but considering the almost complete entry core
  rewrite, the amount of fixes to follow is somewhat higher than usual,
  which is to be expected.

  Peter Zijlstra says:
   'These patches address a number of instrumentation issues that were
    found after the x86/entry overhaul. When combined with rcu/urgent
    and objtool/urgent, these patches make UBSAN/KASAN/KCSAN happy
    again.

    Part of making this all work is bumping the minimum GCC version for
    KASAN builds to gcc-8.3, the reason for this is that the
    __no_sanitize_address function attribute is broken in GCC releases
    before that.

    No known GCC version has a working __no_sanitize_undefined, however
    because the only noinstr violation that results from this happens
    when an UB is found, we treat it like WARN. That is, we allow it to
    violate the noinstr rules in order to get the warning out'"

* tag 'x86_entry_for_5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/entry: Fix #UD vs WARN more
  x86/entry: Increase entry_stack size to a full page
  x86/entry: Fixup bad_iret vs noinstr
  objtool: Don't consider vmlinux a C-file
  kasan: Fix required compiler version
  compiler_attributes.h: Support no_sanitize_undefined check with GCC 4
  x86/entry, bug: Comment the instrumentation_begin() usage for WARN()
  x86/entry, ubsan, objtool: Whitelist __ubsan_handle_*()
  x86/entry, cpumask: Provide non-instrumented variant of cpu_is_offline()
  compiler_types.h: Add __no_sanitize_{address,undefined} to noinstr
  kasan: Bump required compiler version
  x86, kcsan: Add __no_kcsan to noinstr
  kcsan: Remove __no_kcsan_or_inline
  x86, kcsan: Remove __no_kcsan_or_inline usage

Some performance regression on reaim benchmark have been raised with
  commit 070f5e86 ("sched/fair: Take into account runnable_avg to classify group")

The problem comes from the init value of runnable_avg which is initialized
with max value. This can be a problem if the newly forked task is finally
a short task because the group of CPUs is wrongly set to overloaded and
tasks are pulled less agressively.

Set initial value of runnable_avg equals to util_avg to reflect that there
is no waiting time so far.

Fixes: 070f5e86 ("sched/fair: Take into account runnable_avg to classify group")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200624154422.29166-1-vincent.guittot@linaro.org

Instead of relying on BUG_ON() to ensure the various data structures
line up, use a bunch of horrible unions to make it all automatic.

Much of the union magic is to ensure irq_work and smp_call_function do
not (yet) see the members of their respective data structures change
name.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20200622100825.844455025@infradead.org

Use a better name for this poorly named flag, to avoid confusion...
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20200622100825.785115830@infradead.org

Paul reported rcutorture occasionally hitting a NULL deref:

  sched_ttwu_pending()
    ttwu_do_wakeup()
      check_preempt_curr() := check_preempt_wakeup()
        find_matching_se()
          is_same_group()
            if (se->cfs_rq == pse->cfs_rq) <-- *BOOM*

Debugging showed that this only appears to happen when we take the new
code-path from commit:

  2ebb1771 ("sched/core: Offload wakee task activation if it the wakee is descheduling")

and only when @cpu == smp_processor_id(). Something which should not
be possible, because p->on_cpu can only be true for remote tasks.
Similarly, without the new code-path from commit:

  c6e7bd7a ("sched/core: Optimize ttwu() spinning on p->on_cpu")

this would've unconditionally hit:

  smp_cond_load_acquire(&p->on_cpu, !VAL);

and if: 'cpu == smp_processor_id() && p->on_cpu' is possible, this
would result in an instant live-lock (with IRQs disabled), something
that hasn't been reported.

The NULL deref can be explained however if the task_cpu(p) load at the
beginning of try_to_wake_up() returns an old value, and this old value
happens to be smp_processor_id(). Further assume that the p->on_cpu
load accurately returns 1, it really is still running, just not here.

Then, when we enqueue the task locally, we can crash in exactly the
observed manner because p->se.cfs_rq != rq->cfs_rq, because p's cfs_rq
is from the wrong CPU, therefore we'll iterate into the non-existant
parents and NULL deref.

The closest semi-plausible scenario I've managed to contrive is
somewhat elaborate (then again, actual reproduction takes many CPU
hours of rcutorture, so it can't be anything obvious):

					X->cpu = 1
					rq(1)->curr = X

	CPU0				CPU1				CPU2

					// switch away from X
					LOCK rq(1)->lock
					smp_mb__after_spinlock
					dequeue_task(X)
					  X->on_rq = 9
					switch_to(Z)
					  X->on_cpu = 0
					UNLOCK rq(1)->lock

									// migrate X to cpu 0
									LOCK rq(1)->lock
									dequeue_task(X)
									set_task_cpu(X, 0)
									  X->cpu = 0
									UNLOCK rq(1)->lock

									LOCK rq(0)->lock
									enqueue_task(X)
									  X->on_rq = 1
									UNLOCK rq(0)->lock

	// switch to X
	LOCK rq(0)->lock
	smp_mb__after_spinlock
	switch_to(X)
	  X->on_cpu = 1
	UNLOCK rq(0)->lock

	// X goes sleep
	X->state = TASK_UNINTERRUPTIBLE
	smp_mb();			// wake X
					ttwu()
					  LOCK X->pi_lock
					  smp_mb__after_spinlock

					  if (p->state)

					  cpu = X->cpu; // =? 1

					  smp_rmb()

	// X calls schedule()
	LOCK rq(0)->lock
	smp_mb__after_spinlock
	dequeue_task(X)
	  X->on_rq = 0

					  if (p->on_rq)

					  smp_rmb();

					  if (p->on_cpu && ttwu_queue_wakelist(..)) [*]

					  smp_cond_load_acquire(&p->on_cpu, !VAL)

					  cpu = select_task_rq(X, X->wake_cpu, ...)
					  if (X->cpu != cpu)
	switch_to(Y)
	  X->on_cpu = 0
	UNLOCK rq(0)->lock

However I'm having trouble convincing myself that's actually possible
on x86_64 -- after all, every LOCK implies an smp_mb() there, so if ttwu
observes ->state != RUNNING, it must also observe ->cpu != 1.

(Most of the previous ttwu() races were found on very large PowerPC)

Nevertheless, this fully explains the observed failure case.

Fix it by ordering the task_cpu(p) load after the p->on_cpu load,
which is easy since nothing actually uses @cpu before this.

Fixes: c6e7bd7a ("sched/core: Optimize ttwu() spinning on p->on_cpu")
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200622125649.GC576871@hirez.programming.kicks-ass.net

syzbot reported the following warning:

 WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
 enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504

At deadline.c:628 we have:

 623 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 624 {
 625 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 626 	struct rq *rq = rq_of_dl_rq(dl_rq);
 627
 628 	WARN_ON(dl_se->dl_boosted);
 629 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
        [...]
     }

Which means that setup_new_dl_entity() has been called on a task
currently boosted. This shouldn't happen though, as setup_new_dl_entity()
is only called when the 'dynamic' deadline of the new entity
is in the past w.r.t. rq_clock and boosted tasks shouldn't verify this
condition.

Digging through the PI code I noticed that what above might in fact happen
if an RT tasks blocks on an rt_mutex hold by a DEADLINE task. In the
first branch of boosting conditions we check only if a pi_task 'dynamic'
deadline is earlier than mutex holder's and in this case we set mutex
holder to be dl_boosted. However, since RT 'dynamic' deadlines are only
initialized if such tasks get boosted at some point (or if they become
DEADLINE of course), in general RT 'dynamic' deadlines are usually equal
to 0 and this verifies the aforementioned condition.

Fix it by checking that the potential donor task is actually (even if
temporary because in turn boosted) running at DEADLINE priority before
using its 'dynamic' deadline value.

Fixes: 2d3d891d ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Tested-by: Daniel Wagner <dwagner@suse.de>
Link: https://lkml.kernel.org/r/20181119153201.GB2119@localhost.localdomain

syzbot reported the following warning triggered via SYSC_sched_setattr():

  WARNING: CPU: 0 PID: 6973 at kernel/sched/deadline.c:593 setup_new_dl_entity /kernel/sched/deadline.c:594 [inline]
  WARNING: CPU: 0 PID: 6973 at kernel/sched/deadline.c:593 enqueue_dl_entity /kernel/sched/deadline.c:1370 [inline]
  WARNING: CPU: 0 PID: 6973 at kernel/sched/deadline.c:593 enqueue_task_dl+0x1c17/0x2ba0 /kernel/sched/deadline.c:1441

This happens because the ->dl_boosted flag is currently not initialized by
__dl_clear_params() (unlike the other flags) and setup_new_dl_entity()
rightfully complains about it.

Initialize dl_boosted to 0.

Fixes: 2d3d891d ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+5ac8bac25f95e8b221e7@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Daniel Wagner <dwagner@suse.de>
Link: https://lkml.kernel.org/r/20200617072919.818409-1-juri.lelli@redhat.com