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  • Dmitry Baryshkov Dmitry Baryshkov lumag
1 author
  1. Sep 28, 2022
  3. May 17, 2022
  5. Feb 11, 2022
    • Mark Rutland's avatar
      atomics: Fix atomic64_{read_acquire,set_release} fallbacks · dc1b4df0
      Mark Rutland authored 
      
Arnd reports that on 32-bit architectures, the fallbacks for
atomic64_read_acquire() and atomic64_set_release() are broken as they
use smp_load_acquire() and smp_store_release() respectively, which do
not work on types larger than the native word size.

Since those contain compiletime_assert_atomic_type(), any attempt to use
those fallbacks will result in a build-time error. e.g. with the
following added to arch/arm/kernel/setup.c:

| void test_atomic64(atomic64_t *v)
| {
|        atomic64_set_release(v, 5);
|        atomic64_read_acquire(v);
| }

The compiler will complain as follows:

| In file included from <command-line>:
| In function 'arch_atomic64_set_release',
|     inlined from 'test_atomic64' at ./include/linux/atomic/atomic-instrumented.h:669:2:
| ././include/linux/compiler_types.h:346:38: error: call to '__compiletime_assert_9' declared with attribute error: Need native word sized stores/loads for atomicity.
|   346 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|       |                                      ^
| ././include/linux/compiler_types.h:327:4: note: in definition of macro '__compiletime_assert'
|   327 |    prefix ## suffix();    \
|       |    ^~~~~~
| ././include/linux/compiler_types.h:346:2: note: in expansion of macro '_compiletime_assert'
|   346 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|       |  ^~~~~~~~~~~~~~~~~~~
| ././include/linux/compiler_types.h:349:2: note: in expansion of macro 'compiletime_assert'
|   349 |  compiletime_assert(__native_word(t),    \
|       |  ^~~~~~~~~~~~~~~~~~
| ./include/asm-generic/barrier.h:133:2: note: in expansion of macro 'compiletime_assert_atomic_type'
|   133 |  compiletime_assert_atomic_type(*p);    \
|       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| ./include/asm-generic/barrier.h:164:55: note: in expansion of macro '__smp_store_release'
|   164 | #define smp_store_release(p, v) do { kcsan_release(); __smp_store_release(p, v); } while (0)
|       |                                                       ^~~~~~~~~~~~~~~~~~~
| ./include/linux/atomic/atomic-arch-fallback.h:1270:2: note: in expansion of macro 'smp_store_release'
|  1270 |  smp_store_release(&(v)->counter, i);
|       |  ^~~~~~~~~~~~~~~~~
| make[2]: *** [scripts/Makefile.build:288: arch/arm/kernel/setup.o] Error 1
| make[1]: *** [scripts/Makefile.build:550: arch/arm/kernel] Error 2
| make: *** [Makefile:1831: arch/arm] Error 2

Fix this by only using smp_load_acquire() and smp_store_release() for
native atomic types, and otherwise falling back to the regular barriers
necessary for acquire/release semantics, as we do in the more generic
acquire and release fallbacks.

Since the fallback templates are used to generate the atomic64_*() and
atomic_*() operations, the __native_word() check is added to both. For
the atomic_*() operations, which are always 32-bit, the __native_word()
check is redundant but not harmful, as it is always true.

For the example above this works as expected on 32-bit, e.g. for arm
multi_v7_defconfig:

| <test_atomic64>:
|         push    {r4, r5}
|         dmb     ish
|         pldw    [r0]
|         mov     r2, #5
|         mov     r3, #0
|         ldrexd  r4, [r0]
|         strexd  r4, r2, [r0]
|         teq     r4, #0
|         bne     484 <test_atomic64+0x14>
|         ldrexd  r2, [r0]
|         dmb     ish
|         pop     {r4, r5}
|         bx      lr

... and also on 64-bit, e.g. for arm64 defconfig:

| <test_atomic64>:
|         bti     c
|         paciasp
|         mov     x1, #0x5
|         stlr    x1, [x0]
|         ldar    x0, [x0]
|         autiasp
|         ret

Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Reviewed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20220207101943.439825-1-mark.rutland@arm.com
      dc1b4df0
  7. Dec 10, 2021
  9. Jul 16, 2021
  11. May 26, 2021
  13. Nov 07, 2020
    • Ingo Molnar's avatar
      locking/atomics: Regenerate the atomics-check SHA1's · a70a04b3
      Ingo Molnar authored 
      
The include/asm-generic/atomic-instrumented.h checksum got out
of sync, so regenerate it. (No change to actual code.)

Also make scripts/atomic/gen-atomics.sh executable, to make
it easier to use.

The auto-generated atomic header signatures are now fine:

  thule:~/tip> scripts/atomic/check-atomics.sh
  thule:~/tip>

Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      a70a04b3
  15. Oct 12, 2020
  17. Oct 07, 2020
  19. Aug 24, 2020
  21. Jun 25, 2020
  23. Jun 11, 2020
  25. Mar 21, 2020
  27. Jan 07, 2020
  29. Nov 16, 2019
  31. Jun 25, 2019
  33. Apr 19, 2019
  35. Feb 13, 2019
    • Mark Rutland's avatar
      locking/atomics: Check atomic headers with sha1sum · 0cf264b3
      Mark Rutland authored and Ingo Molnar's avatar Ingo Molnar committed 
      
We currently check the atomic headers at build-time to ensure they
haven't been modified directly, and these checks require regenerating
the headers in full. As this takes a few seconds, even when
parallelized, this is too slow to run for every kernel build.

Instead, we can generate a hash of each header as we generate them,
which we can cheaply check at build time (~0.16s for all headers).

This patch does so, updating headers with their hashes using the new
gen-atomics.sh script. As some users apparently build the kernel wihout
coreutils, lacking sha1sum, the checks are skipped in this case.
Presumably, most developers have a working coreutils installation.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: anders.roxell@linaro.org
Cc: linux-kernel@vger.kernel.rg
Cc: naresh.kamboju@linaro.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      0cf264b3
  37. Feb 11, 2019
  39. Nov 01, 2018
    • Ingo Molnar's avatar
      locking/atomics: Fix scripts/atomic/ script permissions · 4d8e5cd2
      Ingo Molnar authored 
      
Mark all these scripts executable.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: boqun.feng@gmail.com
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      4d8e5cd2
    • Mark Rutland's avatar
      locking/atomics: Check generated headers are up-to-date · 8d325880
      Mark Rutland authored and Ingo Molnar's avatar Ingo Molnar committed 
      
Now that all the generated atomic headers are in place, it would be good
to ensure that:

a) the headers are up-to-date when scripting changes.

b) developers don't directly modify the generated headers.

To ensure both of these properties, let's add a Kbuild step to check
that the generated headers are up-to-date.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Link: http://lkml.kernel.org/r/20180904104830.2975-6-mark.rutland@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      8d325880
    • Mark Rutland's avatar
      locking/atomics: Add common header generation files · ace9bad4
      Mark Rutland authored and Ingo Molnar's avatar Ingo Molnar committed 
      
To minimize repetition, to allow for future rework, and to ensure
regularity of the various atomic APIs, we'd like to automatically
generate (the bulk of) a number of headers related to atomics.

This patch adds the infrastructure to do so, leaving actual conversion
of headers to subsequent patches. This infrastructure consists of:

* atomics.tbl - a table describing the functions in the atomics API,
  with names, prototypes, and metadata describing the variants that
  exist (e.g fetch/return, acquire/release/relaxed). Note that the
  return type is dependent on the particular variant.

* atomic-tbl.sh - a library of routines useful for dealing with
  atomics.tbl (e.g. querying which variants exist, or generating
  argument/parameter lists for a given function variant).

* gen-atomic-fallback.sh - a script which generates a header of
  fallbacks, covering cases where architecture omit certain functions
  (e.g. omitting relaxed variants).

* gen-atomic-long.sh - a script which generates wrappers providing the
  atomic_long API atomic of the relevant atomic or atomic64 API,
  ensuring the APIs are consistent.

* gen-atomic-instrumented.sh - a script which generates atomic* wrappers
  atop of arch_atomic* functions, with automatically generated KASAN
  instrumentation.

* fallbacks/* - a set of fallback implementations for atomics, which
  should be used when no implementation of a given atomic is provided.
  These are used by gen-atomic-fallback.sh to generate fallbacks, and
  these are also used by other scripts to determine the set of optional
  atomics (as required to generate preprocessor guards correctly).

  Fallbacks may use the following variables:

  ${atomic}     atomic prefix: atomic/atomic64/atomic_long, which can be
		used to derive the atomic type, and to prefix functions

  ${int}        integer type: int/s64/long

  ${pfx}        variant prefix, e.g. fetch_

  ${name}       base function name, e.g. add

  ${sfx}        variant suffix, e.g. _return

  ${order}      order suffix, e.g. _relaxed

  ${atomicname} full name, e.g. atomic64_fetch_add_relaxed

  ${ret}        return type of the function, e.g. void

  ${retstmt}    a return statement (with a trailing space), unless the
                variant returns void

  ${params}     parameter list for the function declaration, e.g.
                "int i, atomic_t *v"

  ${args}       argument list for invoking the function, e.g. "i, v"

  ... for clarity, ${ret}, ${retstmt}, ${params}, and ${args} are
  open-coded for fallbacks where these do not vary, or are critical to
  understanding the logic of the fallback.

The MAINTAINERS entry for the atomic infrastructure is updated to cover
the new scripts.

There should be no functional change as a result of this patch.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: arnd@arndb.de
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Link: http://lkml.kernel.org/r/20180904104830.2975-2-mark.rutland@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      ace9bad4