[OE-core] [PATCH 1/1] db: disable the ARM assembler mutex code

[Andre McCurdy]

On Thu, Jun 14, 2018 at 9:40 AM, Khem Raj <raj.khem at gmail.com> wrote:
> On 6/14/18 5:10 AM, Herve Jourdain wrote:
>> Hi,
>>
>> I believe I solved that same problem by just adding, in the case of armv8
>> (which I believe may be the new architecture you're referring to):
>> MUTEX_armv8 = ""
>> This way, it allows previous versions to work just like they did before,
>> without having to disable ARM assembler mutex code for architectures that
>> support it correctly - up to armv7ve I believe.
>> Of course, we might need to also have a good definition for armv8, which is
>> the object of another thread.
>
> right thats a better approach.

SWP is not guaranteed to work on SMP systems... and even if it does,
performance is likely to be worse than the pthreads version (which can
take advantage of the newer instructions).

  https://community.arm.com/processors/b/blog/posts/locks-swps-and-two-smoking-barriers

In general, use of hand optimised assembler mutex implementations in
user space isn't something to be encouraged - use pthreads (or maybe a
gcc intrinsic) instead.

I think the original patch is good.

>> Cheers,
>> Herve
>>
>> -----Original Message-----
>> From: openembedded-core-bounces at lists.openembedded.org
>> [mailto:openembedded-core-bounces at lists.openembedded.org] On Behalf Of
>> Ovidiu Panait
>> Sent: jeudi 14 juin 2018 13:55
>> To: openembedded-core at lists.openembedded.org
>> Subject: [OE-core] [PATCH 1/1] db: disable the ARM assembler mutex code
>>
>> The swpb in macro MUTEX_SET will cause "undefined instruction" error on the
>> new arm arches which don't support this assembly instruction any more. If
>> use ldrex/strex to replace swpb, the old arm arches don't support them. So
>> to avoid this issue, just disable the ARM assembler mutex code, and use the
>> default pthreads mutex.
>>
>> Signed-off-by: Li Zhou <li.zhou at windriver.com>
>> Signed-off-by: Catalin Enache <catalin.enache at windriver.com>
>> Signed-off-by: Ovidiu Panait <ovidiu.panait at windriver.com>
>> ---
>>  meta/recipes-support/db/db_5.3.28.bb | 13 +------------
>>  1 file changed, 1 insertion(+), 12 deletions(-)
>>
>> diff --git a/meta/recipes-support/db/db_5.3.28.bb
>> b/meta/recipes-support/db/db_5.3.28.bb
>> index 093ee44909..15b4155a29 100644
>> --- a/meta/recipes-support/db/db_5.3.28.bb
>> +++ b/meta/recipes-support/db/db_5.3.28.bb
>> @@ -59,18 +59,7 @@ FILES_SOLIBSDEV = "${libdir}/libdb.so
>> ${libdir}/libdb_cxx.so"
>>  # All the --disable-* options replace --enable-smallbuild, which breaks a
>> bunch of stuff (eg. postfix)  DB5_CONFIG ?= "--enable-o_direct
>> --disable-cryptography --disable-queue --disable-replication
>> --disable-verify --disable-compat185 --disable-sql"
>>
>> -EXTRA_OECONF = "${DB5_CONFIG} --enable-shared --enable-cxx --with-sysroot"
>> -
>> -# Override the MUTEX setting here, the POSIX library is -# the default -
>> "POSIX/pthreads/library".
>> -# Don't ignore the nice SWP instruction on the ARM:
>> -# These enable the ARM assembler mutex code, this won't -# work with thumb
>> compilation...
>> -ARM_MUTEX = "--with-mutex=ARM/gcc-assembly"
>> -MUTEX = ""
>> -MUTEX_arm = "${ARM_MUTEX}"
>> -MUTEX_armeb = "${ARM_MUTEX}"
>> -EXTRA_OECONF += "${MUTEX} STRIP=true"
>> +EXTRA_OECONF = "${DB5_CONFIG} --enable-shared --enable-cxx --with-sysroot
>> STRIP=true"
>>  EXTRA_OEMAKE += "LIBTOOL='./${HOST_SYS}-libtool'"
>>
>>  EXTRA_AUTORECONF += "--exclude=autoheader  -I ${S}/dist/aclocal
>> -I${S}/dist/aclocal_java"
>> --
>> 2.17.1
>>
>> --
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>> Openembedded-core at lists.openembedded.org
>> http://lists.openembedded.org/mailman/listinfo/openembedded-core
>>
>
>
>
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