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Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details you
should have received a copy of the gnu general public license along
with this program if not you can access it online at http www gnu
org licenses gpl 2 0 html
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190519154041.430943677@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Add SPDX license identifiers to all files which:
- Have no license information of any form
- Have EXPORT_.*_SYMBOL_GPL inside which was used in the
initial scan/conversion to ignore the file
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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During my rwsem testing, it was found that after a down_read(), the
reader count may occasionally become 0 or even negative. Consequently,
a writer may steal the lock at that time and execute with the reader
in parallel thus breaking the mutual exclusion guarantee of the write
lock. In other words, both readers and writer can become rwsem owners
simultaneously.
The current reader wakeup code does it in one pass to clear waiter->task
and put them into wake_q before fully incrementing the reader count.
Once waiter->task is cleared, the corresponding reader may see it,
finish the critical section and do unlock to decrement the count before
the count is incremented. This is not a problem if there is only one
reader to wake up as the count has been pre-incremented by 1. It is
a problem if there are more than one readers to be woken up and writer
can steal the lock.
The wakeup was actually done in 2 passes before the following v4.9 commit:
70800c3c0cc5 ("locking/rwsem: Scan the wait_list for readers only once")
To fix this problem, the wakeup is now done in two passes
again. In the first pass, we collect the readers and count them.
The reader count is then fully incremented. In the second pass, the
waiter->task is then cleared and they are put into wake_q to be woken
up later.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Fixes: 70800c3c0cc5 ("locking/rwsem: Scan the wait_list for readers only once")
Link: http://lkml.kernel.org/r/20190428212557.13482-2-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull mmiowb removal from Will Deacon:
"Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb())
Remove mmiowb() from the kernel memory barrier API and instead, for
architectures that need it, hide the barrier inside spin_unlock() when
MMIO has been performed inside the critical section.
The only relatively recent changes have been addressing review
comments on the documentation, which is in a much better shape thanks
to the efforts of Ben and Ingo.
I was initially planning to split this into two pull requests so that
you could run the coccinelle script yourself, however it's been plain
sailing in linux-next so I've just included the whole lot here to keep
things simple"
* tag 'arm64-mmiowb' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (23 commits)
docs/memory-barriers.txt: Update I/O section to be clearer about CPU vs thread
docs/memory-barriers.txt: Fix style, spacing and grammar in I/O section
arch: Remove dummy mmiowb() definitions from arch code
net/ethernet/silan/sc92031: Remove stale comment about mmiowb()
i40iw: Redefine i40iw_mmiowb() to do nothing
scsi/qla1280: Remove stale comment about mmiowb()
drivers: Remove explicit invocations of mmiowb()
drivers: Remove useless trailing comments from mmiowb() invocations
Documentation: Kill all references to mmiowb()
riscv/mmiowb: Hook up mmwiob() implementation to asm-generic code
powerpc/mmiowb: Hook up mmwiob() implementation to asm-generic code
ia64/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()
mips/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()
sh/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()
m68k/io: Remove useless definition of mmiowb()
nds32/io: Remove useless definition of mmiowb()
x86/io: Remove useless definition of mmiowb()
arm64/io: Remove useless definition of mmiowb()
ARM/io: Remove useless definition of mmiowb()
mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors
...
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git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Martin Schwidefsky:
- Support for kernel address space layout randomization
- Add support for kernel image signature verification
- Convert s390 to the generic get_user_pages_fast code
- Convert s390 to the stack unwind API analog to x86
- Add support for CPU directed interrupts for PCI devices
- Provide support for MIO instructions to the PCI base layer, this will
allow the use of direct PCI mappings in user space code
- Add the basic KVM guest ultravisor interface for protected VMs
- Add AT_HWCAP bits for several new hardware capabilities
- Update the CPU measurement facility counter definitions to SVN 6
- Arnds cleanup patches for his quest to get LLVM compiles working
- A vfio-ccw update with bug fixes and support for halt and clear
- Improvements for the hardware TRNG code
- Another round of cleanup for the QDIO layer
- Numerous cleanups and bug fixes
* tag 's390-5.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (98 commits)
s390/vdso: drop unnecessary cc-ldoption
s390: fix clang -Wpointer-sign warnigns in boot code
s390: drop CONFIG_VIRT_TO_BUS
s390: boot, purgatory: pass $(CLANG_FLAGS) where needed
s390: only build for new CPUs with clang
s390: simplify disabled_wait
s390/ftrace: use HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
s390/unwind: introduce stack unwind API
s390/opcodes: add missing instructions to the disassembler
s390/bug: add entry size to the __bug_table section
s390: use proper expoline sections for .dma code
s390/nospec: rename assembler generated expoline thunks
s390: add missing ENDPROC statements to assembler functions
locking/lockdep: check for freed initmem in static_obj()
s390/kernel: add support for kernel address space layout randomization (KASLR)
s390/kernel: introduce .dma sections
s390/sclp: do not use static sccbs
s390/kprobes: use static buffer for insn_page
s390/kernel: convert SYSCALL and PGM_CHECK handlers to .quad
s390/kernel: build a relocatable kernel
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
"Here are the locking changes in this cycle:
- rwsem unification and simpler micro-optimizations to prepare for
more intrusive (and more lucrative) scalability improvements in
v5.3 (Waiman Long)
- Lockdep irq state tracking flag usage cleanups (Frederic
Weisbecker)
- static key improvements (Jakub Kicinski, Peter Zijlstra)
- misc updates, cleanups and smaller fixes"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (26 commits)
locking/lockdep: Remove unnecessary unlikely()
locking/static_key: Don't take sleeping locks in __static_key_slow_dec_deferred()
locking/static_key: Factor out the fast path of static_key_slow_dec()
locking/static_key: Add support for deferred static branches
locking/lockdep: Test all incompatible scenarios at once in check_irq_usage()
locking/lockdep: Avoid bogus Clang warning
locking/lockdep: Generate LOCKF_ bit composites
locking/lockdep: Use expanded masks on find_usage_*() functions
locking/lockdep: Map remaining magic numbers to lock usage mask names
locking/lockdep: Move valid_state() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING
locking/rwsem: Prevent unneeded warning during locking selftest
locking/rwsem: Optimize rwsem structure for uncontended lock acquisition
locking/rwsem: Enable lock event counting
locking/lock_events: Don't show pvqspinlock events on bare metal
locking/lock_events: Make lock_events available for all archs & other locks
locking/qspinlock_stat: Introduce generic lockevent_*() counting APIs
locking/rwsem: Enhance DEBUG_RWSEMS_WARN_ON() macro
locking/rwsem: Add debug check for __down_read*()
locking/rwsem: Micro-optimize rwsem_try_read_lock_unqueued()
locking/rwsem: Move rwsem internal function declarations to rwsem-xadd.h
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull stack trace updates from Ingo Molnar:
"So Thomas looked at the stacktrace code recently and noticed a few
weirdnesses, and we all know how such stories of crummy kernel code
meeting German engineering perfection end: a 45-patch series to clean
it all up! :-)
Here's the changes in Thomas's words:
'Struct stack_trace is a sinkhole for input and output parameters
which is largely pointless for most usage sites. In fact if embedded
into other data structures it creates indirections and extra storage
overhead for no benefit.
Looking at all usage sites makes it clear that they just require an
interface which is based on a storage array. That array is either on
stack, global or embedded into some other data structure.
Some of the stack depot usage sites are outright wrong, but
fortunately the wrongness just causes more stack being used for
nothing and does not have functional impact.
Another oddity is the inconsistent termination of the stack trace
with ULONG_MAX. It's pointless as the number of entries is what
determines the length of the stored trace. In fact quite some call
sites remove the ULONG_MAX marker afterwards with or without nasty
comments about it. Not all architectures do that and those which do,
do it inconsistenly either conditional on nr_entries == 0 or
unconditionally.
The following series cleans that up by:
1) Removing the ULONG_MAX termination in the architecture code
2) Removing the ULONG_MAX fixups at the call sites
3) Providing plain storage array based interfaces for stacktrace
and stackdepot.
4) Cleaning up the mess at the callsites including some related
cleanups.
5) Removing the struct stack_trace based interfaces
This is not changing the struct stack_trace interfaces at the
architecture level, but it removes the exposure to the generic
code'"
* 'core-stacktrace-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits)
x86/stacktrace: Use common infrastructure
stacktrace: Provide common infrastructure
lib/stackdepot: Remove obsolete functions
stacktrace: Remove obsolete functions
livepatch: Simplify stack trace retrieval
tracing: Remove the last struct stack_trace usage
tracing: Simplify stack trace retrieval
tracing: Make ftrace_trace_userstack() static and conditional
tracing: Use percpu stack trace buffer more intelligently
tracing: Simplify stacktrace retrieval in histograms
lockdep: Simplify stack trace handling
lockdep: Remove save argument from check_prev_add()
lockdep: Remove unused trace argument from print_circular_bug()
drm: Simplify stacktrace handling
dm persistent data: Simplify stack trace handling
dm bufio: Simplify stack trace retrieval
btrfs: ref-verify: Simplify stack trace retrieval
dma/debug: Simplify stracktrace retrieval
fault-inject: Simplify stacktrace retrieval
mm/page_owner: Simplify stack trace handling
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
"This cycles's RCU changes include:
- a couple of straggling RCU flavor consolidation updates
- SRCU updates
- RCU CPU stall-warning updates
- torture-test updates
- an LKMM commit adding support for synchronize_srcu_expedited()
- documentation updates
- miscellaneous fixes"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
net/ipv4/netfilter: Update comment from call_rcu_bh() to call_rcu()
tools/memory-model: Add support for synchronize_srcu_expedited()
doc/kprobes: Update obsolete RCU update functions
torture: Suppress false-positive CONFIG_INITRAMFS_SOURCE complaint
locktorture: NULL cxt.lwsa and cxt.lrsa to allow bad-arg detection
rcuperf: Fix cleanup path for invalid perf_type strings
rcutorture: Fix cleanup path for invalid torture_type strings
rcutorture: Fix expected forward progress duration in OOM notifier
rcutorture: Remove ->ext_irq_conflict field
rcutorture: Make rcutorture_extend_mask() comment match the code
tools/.../rcutorture: Convert to SPDX license identifier
torture: Don't try to offline the last CPU
rcu: Fix nohz status in stall warning
rcu: Move forward-progress checkers into tree_stall.h
rcu: Move irq-disabled stall-warning checking to tree_stall.h
rcu: Organize functions in tree_stall.h
rcu: Move FAST_NO_HZ stall-warning code to tree_stall.h
rcu: Inline RCU stall-warning info helper functions
rcu: Move rcu_print_task_exp_stall() to tree_exp.h
rcu: Inline RCU task stall-warning helper functions
...
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DEBUG_LOCKS_WARN_ON() already contains an unlikely(), there is no need
for another one.
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: houtao1@huawei.com
Link: http://lkml.kernel.org/r/1556540791-23110-1-git-send-email-zhengbin13@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Replace the indirection through struct stack_trace by using the storage
array based interfaces and storing the information is a small lockdep
specific data structure.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
Cc: David Rientjes <rientjes@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: kasan-dev@googlegroups.com
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: David Sterba <dsterba@suse.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: linux-btrfs@vger.kernel.org
Cc: dm-devel@redhat.com
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: linux-arch@vger.kernel.org
Link: https://lkml.kernel.org/r/20190425094802.891724020@linutronix.de
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There is only one caller which hands in save_trace as function pointer.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
Cc: David Rientjes <rientjes@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: kasan-dev@googlegroups.com
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: David Sterba <dsterba@suse.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: linux-btrfs@vger.kernel.org
Cc: dm-devel@redhat.com
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: linux-arch@vger.kernel.org
Link: https://lkml.kernel.org/r/20190425094802.803362058@linutronix.de
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: linux-mm@kvack.org
Cc: David Rientjes <rientjes@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: kasan-dev@googlegroups.com
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: David Sterba <dsterba@suse.com>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: linux-btrfs@vger.kernel.org
Cc: dm-devel@redhat.com
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: linux-arch@vger.kernel.org
Link: https://lkml.kernel.org/r/20190425094802.716274532@linutronix.de
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The following warning occurred on s390:
WARNING: CPU: 0 PID: 804 at kernel/locking/lockdep.c:1025 lockdep_register_key+0x30/0x150
This is because the check in static_obj() assumes that all memory within
[_stext, _end] belongs to static objects, which at least for s390 isn't
true. The init section is also part of this range, and freeing it allows
the buddy allocator to allocate memory from it. We have virt == phys for
the kernel on s390, so that such allocations would then have addresses
within the range [_stext, _end].
To fix this, introduce arch_is_kernel_initmem_freed(), similar to
arch_is_kernel_text/data(), and add it to the checks in static_obj().
This will always return 0 on architectures that do not define
arch_is_kernel_initmem_freed. On s390, it will return 1 if initmem has
been freed and the address is in the range [__init_begin, __init_end].
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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check_prev_add_irq() tests all incompatible scenarios one after the
other while adding a lock (@next) to a tree dependency (@prev):
LOCK_USED_IN_HARDIRQ vs LOCK_ENABLED_HARDIRQ
LOCK_USED_IN_HARDIRQ_READ vs LOCK_ENABLED_HARDIRQ
LOCK_USED_IN_SOFTIRQ vs LOCK_ENABLED_SOFTIRQ
LOCK_USED_IN_SOFTIRQ_READ vs LOCK_ENABLED_SOFTIRQ
Also for these four scenarios, we must at least iterate the @prev
backward dependency. Then if it matches the relevant LOCK_USED_* bit,
we must also iterate the @next forward dependency.
Therefore in the best case we iterate 4 times, in the worst case 8 times.
A different approach can let us divide the number of branch iterations
by 4:
1) Iterate through @prev backward dependencies and accumulate all the IRQ
uses in a single mask. In the best case where the current lock hasn't
been used in IRQ, we stop here.
2) Iterate through @next forward dependencies and try to find a lock
whose usage is exclusive to the accumulated usages gathered in the
previous step. If we find one (call it @lockA), we have found an
incompatible use, otherwise we stop here. Only bad locking scenario
go further. So a sane verification stop here.
3) Iterate again through @prev backward dependency and find the lock
whose usage matches @lockA in term of incompatibility. Call that
lock @lockB.
4) Report the incompatible usages of @lockA and @lockB
If no incompatible use is found, the verification never goes beyond
step 2 which means at most two iterations.
The following compares the execution measurements of the function
check_prev_add_irq():
Number of calls | Avg (ns) | Stdev (ns) | Total time (ns)
------------------------------------------------------------------------
Mainline 8452 | 2652 | 11962 | 22415143
This patch 8452 | 1518 | 7090 | 12835602
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190402160244.32434-5-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU and LKMM commits from Paul E. McKenney:
- An LKMM commit adding support for synchronize_srcu_expedited()
- A couple of straggling RCU flavor consolidation updates
- Documentation updates.
- Miscellaneous fixes
- SRCU updates
- RCU CPU stall-warning updates
- Torture-test updates
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Instead of open-coding the bitmasks, generate them using the
lockdep_states.h header.
This prepares for additional states, which would make the manual masks
tedious and error prone.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
In order to optimize check_irq_usage() and factorize all the IRQ usage
validations we'll need to be able to check multiple lock usage bits at
once. Prepare the low level usage mask check functions for that purpose.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190402160244.32434-4-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Clarify the code with mapping some more constant numbers that haven't
been named after their corresponding LOCK_USAGE_* symbol.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190402160244.32434-3-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
CONFIG_PROVE_LOCKING
valid_state() and print_usage_bug*() functions are not used beyond
irq locking correctness checks under CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING.
Sadly the "unused function" warning wouldn't fire because valid_state()
is inline so the unused case has remained unseen until now.
So move them inside the appropriate CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING
section.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190402160244.32434-2-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
If lockdep_register_key() and lockdep_unregister_key() are called with
debug_locks == false then the following warning is reported:
WARNING: CPU: 2 PID: 15145 at kernel/locking/lockdep.c:4920 lockdep_unregister_key+0x1ad/0x240
That warning is reported because lockdep_unregister_key() ignores the
value of 'debug_locks' and because the behavior of lockdep_register_key()
depends on whether or not 'debug_locks' is set. Fix this inconsistency
by making lockdep_unregister_key() take 'debug_locks' again into
account.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: shenghui <shhuiw@foxmail.com>
Fixes: 90c1cba2b3b3 ("locking/lockdep: Zap lock classes even with lock debugging disabled")
Link: http://lkml.kernel.org/r/20190415170538.23491-1-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
No architecture terminates the stack trace with ULONG_MAX anymore. Remove
the cruft.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190410103644.485737321@linutronix.de
|
|
Disable the DEBUG_RWSEMS check when locking selftest is running with
debug_locks_silent flag set.
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Link: http://lkml.kernel.org/r/20190413172259.2740-2-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
The following commit:
a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use")
changed the behavior of lockdep_free_key_range() from
unconditionally zapping lock classes into only zapping lock classes if
debug_lock == true. Not zapping lock classes if debug_lock == false leaves
dangling pointers in several lockdep datastructures, e.g. lock_class::name
in the all_lock_classes list.
The shell command "cat /proc/lockdep" causes the kernel to iterate the
all_lock_classes list. Hence the "unable to handle kernel paging request" cash
that Shenghui encountered by running cat /proc/lockdep.
Since the new behavior can cause cat /proc/lockdep to crash, restore the
pre-v5.1 behavior.
This patch avoids that cat /proc/lockdep triggers the following crash
with debug_lock == false:
BUG: unable to handle kernel paging request at fffffbfff40ca448
RIP: 0010:__asan_load1+0x28/0x50
Call Trace:
string+0xac/0x180
vsnprintf+0x23e/0x820
seq_vprintf+0x82/0xc0
seq_printf+0x92/0xb0
print_name+0x34/0xb0
l_show+0x184/0x200
seq_read+0x59e/0x6c0
proc_reg_read+0x11f/0x170
__vfs_read+0x4d/0x90
vfs_read+0xc5/0x1f0
ksys_read+0xab/0x130
__x64_sys_read+0x43/0x50
do_syscall_64+0x71/0x210
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Reported-by: shenghui <shhuiw@foxmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
Link: https://lkml.kernel.org/r/20190403233552.124673-1-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Add lock event counting calls so that we can track the number of lock
events happening in the rwsem code.
With CONFIG_LOCK_EVENT_COUNTS on and booting a 4-socket 112-thread x86-64
system, the rwsem counts after system bootup were as follows:
rwsem_opt_fail=261
rwsem_opt_wlock=50636
rwsem_rlock=445
rwsem_rlock_fail=0
rwsem_rlock_fast=22
rwsem_rtrylock=810144
rwsem_sleep_reader=441
rwsem_sleep_writer=310
rwsem_wake_reader=355
rwsem_wake_writer=2335
rwsem_wlock=261
rwsem_wlock_fail=0
rwsem_wtrylock=20583
It can be seen that most of the lock acquisitions in the slowpath were
write-locks in the optimistic spinning code path with no sleeping at
all. For this system, over 97% of the locks are acquired via optimistic
spinning. It illustrates the importance of optimistic spinning in
improving the performance of rwsem.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-11-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
On bare metal, the pvqspinlock event counts will always be 0. So there
is no point in showing their corresponding debugfs files. So they are
skipped in this case.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-10-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
The QUEUED_LOCK_STAT option to report queued spinlocks event counts
was previously allowed only on x86 architecture. To make the locking
event counting code more useful, it is now renamed to a more generic
LOCK_EVENT_COUNTS config option. This new option will be available to
all the architectures that use qspinlock at the moment.
Other locking code can now start to use the generic locking event
counting code by including lock_events.h and put the new locking event
names into the lock_events_list.h header file.
My experience with lock event counting is that it gives valuable insight
on how the locking code works and what can be done to make it better. I
would like to extend this benefit to other locking code like mutex and
rwsem in the near future.
The PV qspinlock specific code will stay in qspinlock_stat.h. The
locking event counters will now reside in the <debugfs>/lock_event_counts
directory.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-9-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
The percpu event counts used by qspinlock code can be useful for
other locking code as well. So a new set of lockevent_* counting APIs
is introduced with the lock event names extracted out into the new
lock_events_list.h header file for easier addition in the future.
The existing qstat_inc() calls are replaced by either lockevent_inc() or
lockevent_cond_inc() calls.
The qstat_hop() call is renamed to lockevent_pv_hop(). The "reset_counters"
debugfs file is also renamed to ".reset_counts".
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-8-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Currently, the DEBUG_RWSEMS_WARN_ON() macro just dumps a stack trace
when the rwsem isn't in the right state. It does not show the actual
states of the rwsem. This may not be that helpful in the debugging
process.
Enhance the DEBUG_RWSEMS_WARN_ON() macro to also show the current
content of the rwsem count and owner fields to give more information
about what is wrong with the rwsem. The debug_locks_off() function is
called as is done inside DEBUG_LOCKS_WARN_ON().
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-7-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
When rwsem_down_read_failed*() return, the read lock is acquired
indirectly by others. So debug checks are added in __down_read() and
__down_read_killable() to make sure the rwsem is really reader-owned.
The other debug check calls in kernel/locking/rwsem.c except the
one in up_read_non_owner() are also moved over to rwsem-xadd.h.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-6-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
The atomic_long_cmpxchg_acquire() in rwsem_try_read_lock_unqueued() is
replaced by atomic_long_try_cmpxchg_acquire() to simpify the code and
generate slightly better assembly code.
There is no functional change.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-5-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
We don't need to expose rwsem internal functions which are not supposed
to be called directly from other kernel code.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-4-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Move all the owner setting code closer to the rwsem-xadd fast paths
directly within rwsem.h file as well as in the slowpaths where owner
setting is done after acquring the lock. This will enable us to add
DEBUG_RWSEMS check in a later patch to make sure that read lock is
really acquired when rwsem_down_read_failed() returns, for instance.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-3-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
The rwsem_down_read_failed*() functions were relocated from above the
optimistic spinning section to below that section. This enables the
reader functions to use optimisitic spinning in future patches. There
is no code change.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-2-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Removing explicit calls to mmiowb() from driver code means that we must
now call into the generic mmiowb_spin_{lock,unlock}() functions from the
core spinlock code. In order to elide barriers following critical
sections without any I/O writes, we also hook into the asm-generic I/O
routines.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
|
|
In preparation for removing all explicit mmiowb() calls from driver
code, implement a tracking system in asm-generic based loosely on the
PowerPC implementation. This allows architectures with a non-empty
mmiowb() definition to have the barrier automatically inserted in
spin_unlock() following a critical section containing an I/O write.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
|
|
Modify __down_read_trylock() to optimize for an unlocked rwsem and make
it generate slightly better code.
Before this patch, down_read_trylock:
0x0000000000000000 <+0>: callq 0x5 <down_read_trylock+5>
0x0000000000000005 <+5>: jmp 0x18 <down_read_trylock+24>
0x0000000000000007 <+7>: lea 0x1(%rdx),%rcx
0x000000000000000b <+11>: mov %rdx,%rax
0x000000000000000e <+14>: lock cmpxchg %rcx,(%rdi)
0x0000000000000013 <+19>: cmp %rax,%rdx
0x0000000000000016 <+22>: je 0x23 <down_read_trylock+35>
0x0000000000000018 <+24>: mov (%rdi),%rdx
0x000000000000001b <+27>: test %rdx,%rdx
0x000000000000001e <+30>: jns 0x7 <down_read_trylock+7>
0x0000000000000020 <+32>: xor %eax,%eax
0x0000000000000022 <+34>: retq
0x0000000000000023 <+35>: mov %gs:0x0,%rax
0x000000000000002c <+44>: or $0x3,%rax
0x0000000000000030 <+48>: mov %rax,0x20(%rdi)
0x0000000000000034 <+52>: mov $0x1,%eax
0x0000000000000039 <+57>: retq
After patch, down_read_trylock:
0x0000000000000000 <+0>: callq 0x5 <down_read_trylock+5>
0x0000000000000005 <+5>: xor %eax,%eax
0x0000000000000007 <+7>: lea 0x1(%rax),%rdx
0x000000000000000b <+11>: lock cmpxchg %rdx,(%rdi)
0x0000000000000010 <+16>: jne 0x29 <down_read_trylock+41>
0x0000000000000012 <+18>: mov %gs:0x0,%rax
0x000000000000001b <+27>: or $0x3,%rax
0x000000000000001f <+31>: mov %rax,0x20(%rdi)
0x0000000000000023 <+35>: mov $0x1,%eax
0x0000000000000028 <+40>: retq
0x0000000000000029 <+41>: test %rax,%rax
0x000000000000002c <+44>: jns 0x7 <down_read_trylock+7>
0x000000000000002e <+46>: xor %eax,%eax
0x0000000000000030 <+48>: retq
By using a rwsem microbenchmark, the down_read_trylock() rate (with a
load of 10 to lengthen the lock critical section) on a x86-64 system
before and after the patch were:
Before Patch After Patch
# of Threads rlock rlock
------------ ----- -----
1 14,496 14,716
2 8,644 8,453
4 6,799 6,983
8 5,664 7,190
On a ARM64 system, the performance results were:
Before Patch After Patch
# of Threads rlock rlock
------------ ----- -----
1 23,676 24,488
2 7,697 9,502
4 4,945 3,440
8 2,641 1,603
For the uncontended case (1 thread), the new down_read_trylock() is a
little bit faster. For the contended cases, the new down_read_trylock()
perform pretty well in x86-64, but performance degrades at high
contention level on ARM64.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-um@lists.infradead.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: nios2-dev@lists.rocketboards.org
Cc: openrisc@lists.librecor |
