The volatile attribute in the inline assembly of arch_raw_cpu_ptr()
forces the compiler to always generate the code, even if the compiler
can decide upfront that its result is not needed.
For instance invoking __intel_pmu_disable_all(false) (like
intel_pmu_snapshot_arch_branch_stack() does) leads to loading the
address of &cpu_hw_events into the register while compiler knows that it
has no need for it. This ends up with code like:
| movq $cpu_hw_events, %rax #, tcp_ptr__
| add %gs:this_cpu_off(%rip), %rax # this_cpu_off, tcp_ptr__
| xorl %eax, %eax # tmp93
It also creates additional code within local_lock() with !RT &&
!LOCKDEP which is not desired.
By removing the volatile attribute the compiler can place the
function freely and avoid it if it is not needed in the end.
By using the function twice the compiler properly caches only the
variable offset and always loads the CPU-offset.
this_cpu_ptr() also remains properly placed within a preempt_disable()
sections because
- arch_raw_cpu_ptr() assembly has a memory input ("m" (this_cpu_off))
- prempt_{dis,en}able() fundamentally has a 'barrier()' in it
Therefore this_cpu_ptr() is already properly serialized and does not
rely on the 'volatile' attribute.
Remove volatile from arch_raw_cpu_ptr().
[ bigeasy: Added Linus' explanation why this_cpu_ptr() is not moved out
of a preempt_disable() section without the 'volatile' attribute. ]
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220328145810.86783-2-bigeasy@linutronix.de
Also remove now unused __percpu_mov_op.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-11-ndesaulniers@google.com
Use __pcpu_size_call_return() to simplify this_cpu_read_stable().
Also remove __bad_percpu_size() which is now unused.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-10-ndesaulniers@google.com
The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.
Also use appropriate types for the width of the instructions. This avoids
errors when compiling with Clang.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-9-ndesaulniers@google.com
The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.
Also use appropriate types for the width of the instructions. This avoids
errors when compiling with Clang.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-8-ndesaulniers@google.com
The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.
Also use appropriate types for the width of the instructions. This avoids
errors when compiling with Clang.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-7-ndesaulniers@google.com
The "e" constraint represents a constant, but the XADD instruction doesn't
accept immediate operands.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-6-ndesaulniers@google.com
The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.
Also use appropriate types for the width of the instructions. This avoids
errors when compiling with Clang.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-5-ndesaulniers@google.com
The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.
Also use appropriate types for the width of the instructions. This avoids
errors when compiling with Clang.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-4-ndesaulniers@google.com
The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.
Also use appropriate types for the width of the instructions. This avoids
errors when compiling with Clang.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-3-ndesaulniers@google.com
In preparation for cleaning up the percpu operations, define macros for
abstraction based on the width of the operation.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-2-ndesaulniers@google.com
Since raw_cpu_xchg() doesn't need to be IRQ-safe, like
this_cpu_xchg(), we can use a simple load-store instead of the cmpxchg
loop.
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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Eric reported that a sequence count loop using this_cpu_read() got
optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
because the interface is IRQ-safe, therefore an interrupt can have
changed the per-cpu value.
Fixes: 7c3576d261 ("[PATCH] i386: Convert PDA into the percpu section")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Cc: hpa@zytor.com
Cc: eric.dumazet@gmail.com
Cc: bp@alien8.de
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181011104019.748208519@infradead.org
Use CC_SET(z)/CC_OUT(z) instead of explicit SETZ instruction.
Using these two defines, the compiler that supports generation of
condition code outputs from inline assembly flags generates e.g.:
cmpxchg8b %fs:(%esi)
jne 172255 <__kmalloc+0x65>
instead of:
cmpxchg8b %fs:(%esi)
sete %al
test %al,%al
je 172255 <__kmalloc+0x65>
Note that older compilers now generate:
cmpxchg8b %fs:(%esi)
sete %cl
test %cl,%cl
je 173a85 <__kmalloc+0x65>
since we have to mark that cmpxchg8b instruction outputs to %eax
register and this way clobbers the value in the register.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20180605163910.13015-1-ubizjak@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Omitting suffixes from instructions in AT&T mode is bad practice when
operand size cannot be determined by the assembler from register
operands, and is likely going to be warned about by upstream gas in the
future (mine does already). Add the missing suffixes here. Note that for
64-bit this means some operations change from being 32-bit to 64-bit.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/5A93F98702000078001ABACC@prv-mh.provo.novell.com
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There is no need for \n\t in front of CC_SET(), as the macro already includes these two.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170906151808.5634-1-ubizjak@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Remove open-coded uses of set instructions to use CC_SET()/CC_OUT() in
<asm/percpu.h>.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1465414726-197858-8-git-send-email-hpa@linux.intel.com
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
The gcc people have confirmed that using "bool" when combined with
inline assembly always is treated as a byte-sized operand that can be
assumed to be 0 or 1, which is exactly what the SET instruction
emits. Change the output types and intermediate variables of as many
operations as practical to "bool".
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1465414726-197858-3-git-send-email-hpa@linux.intel.com
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Use SETC instead of SBB to return the value of CF from assembly. Using
SETcc enables uniformity with other flags-returning pieces of assembly
code.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1465414726-197858-2-git-send-email-hpa@linux.intel.com
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Observing that per-CPU data (in the SMP case) is reachable by
exploiting 64-bit address wraparound (building on the default kernel
load address being at 16Mb), the one byte shorter RIP-relative
addressing form can be used for most per-CPU accesses. The one
exception are the "stable" reads, where the use of the "P" operand
modifier prevents the compiler from using RIP-relative addressing, but
is unavoidable due to the use of the "p" constraint (side note: with
gcc 4.9.x the intended effect of this isn't being achieved anymore,
see gcc bug 63637).
With the dependency on the minimum kernel load address, arbitrarily
low values for CONFIG_PHYSICAL_START are now no longer possible. A
link time assertion is being added, directing to the need to increase
that value when it triggers.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/5458A1780200007800044A9D@mail.emea.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Both this_cpu_off and cpu_info aren't getting modified post boot, yet
are being accessed on enough code paths that grouping them with other
frequently read items seems desirable. For cpu_info this at the same
time implies removing the cache line alignment (which afaict became
pointless when it got converted to per-CPU data years ago).
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/54589BD20200007800044A84@mail.emea.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
__verify_pcpu_ptr() is used to verify that a specified parameter is
actually an percpu pointer by percpu accessor and operation
implementations. Currently, where it's called isn't clearly defined
and we just ensure that it's invoked at least once for all accessors
and operations.
The lack of clarity on when it should be called isn't nice and given
that this is a completely generic issue, there's no reason to make
archs worry about it.
This patch updates __verify_pcpu_ptr() invocations such that it's
always invoked from the final generic wrapper once per access or
operation. As this is already the case for {raw|this}_cpu_*()
definitions through __pcpu_size_*(), only the {raw|per|this}_cpu_ptr()
accessors need to be updated.
This change makes it unnecessary for archs to worry about
__verify_pcpu_ptr(). x86's arch_raw_cpu_ptr() is updated accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Currently, archs can override raw_cpu_ptr() directly; however, we
wanna build a layer of indirection in the generic part of percpu so
that we can implement generic features there without affecting archs.
Introduce arch_raw_cpu_ptr() which is used to define raw_cpu_ptr() by
generic percpu code. The two are identical for now. x86 is currently
the only arch which overrides raw_cpu_ptr() and is converted to
define arch_raw_cpu_ptr() instead.
This doesn't introduce any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
The kernel has never been audited to ensure that this_cpu operations are
consistently used throughout the kernel. The code generated in many
places can be improved through the use of this_cpu operations (which
uses a segment register for relocation of per cpu offsets instead of
performing address calculations).
The patch set also addresses various consistency issues in general with
the per cpu macros.
A. The semantics of __this_cpu_ptr() differs from this_cpu_ptr only
because checks are skipped. This is typically shown through a raw_
prefix. So this patch set changes the places where __this_cpu_ptr()
is used to raw_cpu_ptr().
B. There has been the long term wish by some that __this_cpu operations
would check for preemption. However, there are cases where preemption
checks need to be skipped. This patch set adds raw_cpu operations that
do not check for preemption and then adds preemption checks to the
__this_cpu operations.
C. The use of __get_cpu_var is always a reference to a percpu variable
that can also be handled via a this_cpu operation. This patch set
replaces all uses of __get_cpu_var with this_cpu operations.
D. We can then use this_cpu RMW operations in various places replacing
sequences of instructions by a single one.
E. The use of this_cpu operations throughout will allow other arches than
x86 to implement optimized references and RMV operations to work with
per cpu local data.
F. The use of this_cpu operations opens up the possibility to
further optimize code that relies on synchronization through
per cpu data.
The patch set works in a couple of stages:
I. Patch 1 adds the additional raw_cpu operations and raw_cpu_ptr().
Also converts the existing __this_cpu_xx_# primitive in the x86
code to raw_cpu_xx_#.
II. Patch 2-4 use the raw_cpu operations in places that would give
us false positives once they are enabled.
III. Patch 5 adds preemption checks to __this_cpu operations to allow
checking if preemption is properly disabled when these functions
are used.
IV. Patches 6-20 are patches that simply replace uses of __get_cpu_var
with this_cpu_ptr. They do not depend on any changes to the percpu
code. No preemption tests are skipped if they are applied.
V. Patches 21-46 are conversion patches that use this_cpu operations
in various kernel subsystems/drivers or arch code.
VI. Patches 47/48 (not included in this series) remove no longer used
functions (__this_cpu_ptr and __get_cpu_var). These should only be
applied after all the conversion patches have made it and after we
have done additional passes through the kernel to ensure that none of
the uses of these functions remain.
This patch (of 46):
The patches following this one will add preemption checks to __this_cpu
ops so we need to have an alternative way to use this_cpu operations
without preemption checks.
raw_cpu_ops will be the basis for all other ops since these will be the
operations that do not implement any checks.
Primitive operations are renamed by this patch from __this_cpu_xxx to
raw_cpu_xxxx.
Also change the uses of the x86 percpu primitives in preempt.h.
These depend directly on asm/percpu.h (header #include nesting issue).
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Alex Shi <alex.shi@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: David Daney <david.daney@cavium.com>
Cc: David Miller <davem@davemloft.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Haavard Skinnemoen <hskinnemoen@gmail.com>
Cc: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Hedi Berriche <hedi@sgi.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Mike Travis <travis@sgi.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Robert Richter <rric@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull percpu changes from Tejun Heo:
"Two smallish changes for percpu. Two patches to remove unused
this_cpu_xor() and one to fix a bug in percpu init failure path so
that it can reach the proper BUG() instead of oopsing earlier"
* 'for-3.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
x86: remove this_cpu_xor() implementation
percpu: remove this_cpu_xor() implementation
percpu: fix bootmem error handling in pcpu_page_first_chunk()
this_cpu_sub() is implemented as negation and addition.
This patch casts the adjustment to the counter type before negation to
sign extend the adjustment. This helps in cases where the counter type
is wider than an unsigned adjustment. An alternative to this patch is
to declare such operations unsupported, but it seemed useful to avoid
surprises.
This patch specifically helps the following example:
unsigned int delta = 1
preempt_disable()
this_cpu_write(long_counter, 0)
this_cpu_sub(long_counter, delta)
preempt_enable()
Before this change long_counter on a 64 bit machine ends with value
0xffffffff, rather than 0xffffffffffffffff. This is because
this_cpu_sub(pcp, delta) boils down to this_cpu_add(pcp, -delta),
which is basically:
long_counter = 0 + 0xffffffff
Also apply the same cast to:
__this_cpu_sub()
__this_cpu_sub_return()
this_cpu_sub_return()
All percpu_test.ko passes, especially the following cases which
previously failed:
l -= ui_one;
__this_cpu_sub(long_counter, ui_one);
CHECK(l, long_counter, -1);
l -= ui_one;
this_cpu_sub(long_counter, ui_one);
CHECK(l, long_counter, -1);
CHECK(l, long_counter, 0xffffffffffffffff);
ul -= ui_one;
__this_cpu_sub(ulong_counter, ui_one);
CHECK(ul, ulong_counter, -1);
CHECK(ul, ulong_counter, 0xffffffffffffffff);
ul = this_cpu_sub_return(ulong_counter, ui_one);
CHECK(ul, ulong_counter, 2);
ul = __this_cpu_sub_return(ulong_counter, ui_one);
CHECK(ul, ulong_counter, 1);
Signed-off-by: Greg Thelen <gthelen@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove the unused x86 implementation of this_cpu_xor().
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Some read-mostly per-cpu data may need to be declared or defined
early, so it can be initialized and accessed before per_cpu
areas are allocated.
Only the data that resides in the per_cpu areas should be
read-mostly, as there is little benefit in optimizing cache
lines on initialization.
Signed-off-by: Ido Yariv <ido@wizery.com>
[ Added the missing declarations in !SMP code. ]
Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
Acked-by: Shai Fultheim <shai@scalemp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/46188571.ddB8aVQYWo@vlad
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Remove percpu_xxx serial functions, all of them were replaced by
this_cpu_xxx or __this_cpu_xxx serial functions
Signed-off-by: Alex Shi <alex.shi@intel.com>
Acked-by: Christoph Lameter <cl@gentwo.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since percpu_xxx() serial functions are duplicated with this_cpu_xxx().
Removing percpu_xxx() definition and replacing them by this_cpu_xxx()
in code. There is no function change in this patch, just preparation for
later percpu_xxx serial function removing.
On x86 machine the this_cpu_xxx() serial functions are same as
__this_cpu_xxx() without no unnecessary premmpt enable/disable.
Thanks for Stephen Rothwell, he found and fixed a i386 build error in
the patch.
Also thanks for Andrew Morton, he kept updating the patchset in Linus'
tree.
Signed-off-by: Alex Shi <alex.shi@intel.com>
Acked-by: Christoph Lameter <cl@gentwo.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
* 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
percpu: Remove irqsafe_cpu_xxx variants
Fix up conflict in arch/x86/include/asm/percpu.h due to clash with
cebef5beed ("x86: Fix and improve percpu_cmpxchg{8,16}b_double()")
which edited the (now removed) irqsafe_cpu_cmpxchg*_double code.
We simply say that regular this_cpu use must be safe regardless of
preemption and interrupt state. That has no material change for x86
and s390 implementations of this_cpu operations. However, arches that
do not provide their own implementation for this_cpu operations will
now get code generated that disables interrupts instead of preemption.
-tj: This is part of on-going percpu API cleanup. For detailed
discussion of the subject, please refer to the following thread.
http://thread.gmane.org/gmane.linux.kernel/1222078
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <alpine.DEB.2.00.1112221154380.11787@router.home>
They had several problems/shortcomings:
Only the first memory operand was mentioned in the 2x32bit asm()
operands, and 2x64-bit version had a memory clobber. The first
allowed the compiler to not recognize the need to re-load the
data in case it had it cached in some register, and the second
was overly destructive.
The memory operand in the 2x32-bit asm() was declared to only be
an output.
The types of the local copies of the old and new values were
incorrect (as in other per-CPU ops, the types of the per-CPU
variables accessed should be used here, to make sure the
respective types are compatible).
The __dummy variable was pointless (and needlessly initialized
in the 2x32-bit case), given that local copies of the inputs
already exist.
The 2x64-bit variant forced the address of the first object into
%rsi, even though this is needed only for the call to the
emulation function. The real cmpxchg16b can operate on an
memory.
At once also change the return value type to what it really is -
'bool'.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4EE86D6502000078000679FE@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Somehow we got into a situation where the __this_cpu_xchg() operations were
not defined in the same way as this_cpu_xchg() and friends. I had some build
failures under 32 bit that were addressed by these fixes.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
* 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
percpu: Unify input section names
percpu: Avoid extra NOP in percpu_cmpxchg16b_double
percpu: Cast away printk format warning
percpu: Always align percpu output section to PAGE_SIZE
Fix up fairly trivial conflict in arch/x86/include/asm/percpu.h as per Tejun
* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (50 commits)
x86, mm: Allow ZONE_DMA to be configurable
x86, NUMA: Trim numa meminfo with max_pfn in a separate loop
x86, NUMA: Rename setup_node_bootmem() to setup_node_data()
x86, NUMA: Enable emulation on 32bit too
x86, NUMA: Enable CONFIG_AMD_NUMA on 32bit too
x86, NUMA: Rename amdtopology_64.c to amdtopology.c
x86, NUMA: Make numa_init_array() static
x86, NUMA: Make 32bit use common NUMA init path
x86, NUMA: Initialize and use remap allocator from setup_node_bootmem()
x86-32, NUMA: Add @start and @end to init_alloc_remap()
x86, NUMA: Remove long 64bit assumption from numa.c
x86, NUMA: Enable build of generic NUMA init code on 32bit
x86, NUMA: Move NUMA init logic from numa_64.c to numa.c
x86-32, NUMA: Update numaq to use new NUMA init protocol
x86-32, NUMA: Replace srat_32.c with srat.c
x86-32, NUMA: implement temporary NUMA init shims
x86, NUMA: Move numa_nodes_parsed to numa.[hc]
x86-32, NUMA: Move get_memcfg_numa() into numa_32.c
x86, NUMA: make srat.c 32bit safe
x86, NUMA: rename srat_64.c to srat.c
...
Add this_cpu_has() which determines if the current cpu has a certain
ability using a segment prefix and a bit test operation.
For that we need to add bit operations to x86s percpu.h.
Many uses of cpu_has use a pointer passed to a function to determine
the current flags. That is no longer necessary after this patch.
However, this patch only converts the straightforward cases where
cpu_has is used with this_cpu_ptr. The rest is work for later.
-tj: Rolled up patch to add x86_ prefix and use percpu_read() instead
of percpu_read_stable().
Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Omit the segment prefix in the UP case. GS is not used then
and we will generate segfaults if cmpxchg16b is used otherwise.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-2.6.39' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
percpu, x86: Add arch-specific this_cpu_cmpxchg_double() support
percpu: Generic support for this_cpu_cmpxchg_double()
alpha: use L1_CACHE_BYTES for cacheline size in the linker script
percpu: align percpu readmostly subsection to cacheline
Fix up trivial conflict in arch/x86/kernel/vmlinux.lds.S due to the
percpu alignment having changed ("x86: Reduce back the alignment of the
per-CPU data section")
Support this_cpu_cmpxchg_double() using the cmpxchg16b and cmpxchg8b
instructions.
-tj: s/percpu_cmpxchg16b/percpu_cmpxchg16b_double/ for consistency and
other cosmetic changes.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
These recent percpu commits:
2485b6464cf8: x86,percpu: Move out of place 64 bit ops into X86_64 section
8270137a0d50: cpuops: Use cmpxchg for xchg to avoid lock semantics
Caused this 'perf top' crash:
Kernel panic - not syncing: Fatal exception in interrupt
Pid: 0, comm: swapper Tainted: G D
2.6.38-rc2-00181-gef71723 #413 Call Trace: <IRQ> [<ffffffff810465b5>]
? panic
? kmsg_dump
? kmsg_dump
? oops_end
? no_context
? __bad_area_nosemaphore
? perf_output_begin
? bad_area_nosemaphore
? do_page_fault
? __task_pid_nr_ns
? perf_event_tid
? __perf_event_header__init_id
? validate_chain
? perf_output_sample
? trace_hardirqs_off
? page_fault
? irq_work_run
? update_process_times
? tick_sched_timer
? tick_sched_timer
? __run_hrtimer
? hrtimer_interrupt
? account_system_vtime
? smp_apic_timer_interrupt
? apic_timer_interrupt
...
Looking at assembly code, I found:
list = this_cpu_xchg(irq_work_list, NULL);
gives this wrong code : (gcc-4.1.2 cross compiler)
ffffffff810bc45e:
mov %gs:0xead0,%rax
cmpxchg %rax,%gs:0xead0
jne ffffffff810bc45e <irq_work_run+0x3e>
test %rax,%rax
je ffffffff810bc4aa <irq_work_run+0x8a>
Tell gcc we dirty eax/rax register in percpu_xchg_op()
Compiler must use another register to store pxo_new__
We also dont need to reload percpu value after a jump,
since a 'failed' cmpxchg already updated eax/rax
Wrong generated code was :
xor %rax,%rax /* load 0 into %rax */
1: mov %gs:0xead0,%rax
cmpxchg %rax,%gs:0xead0
jne 1b
test %rax,%rax
After patch :
xor %rdx,%rdx /* load 0 into %rdx */
mov %gs:0xead0,%rax
1: cmpxchg %rdx,%gs:0xead0
jne 1b:
test %rax,%rax
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>
LKML-Reference: <1295973114.3588.312.camel@edumazet-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some operations that operate on 64 bit operands are defined for 32 bit.
Move them into the correct section.
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Sebastian Andrzej Siewior