On 5/31/07, Eduardo Morras <[EMAIL PROTECTED]> wrote:
At 23:25 30/05/2007, you wrote:
>Setting and reading individual bytes (u8 in sqlite-speak) are not
>threadsafe either. Only reading/setting entire entire words
>are threadsafe on most architectures.
Using a uint32 for store the flags is threadsafe. There are less than 32
true/false values and read/set is simple. I see no difference doing
if (uint8==0){ // read/test bit
uint8=1; // set bit
whatever more
}
Not atomic, so not thread-safe.
You have a race condition waiting to happen.
and
if (uint32&&MASK){ // read/test bit
uint32&&=MASK; // set bit
whatever
}
Also not atomic, so not thread-safe.
in speed, and a compiler should not make worse code on last one. So say
>> Also, my take on bitfields is that they are not thread/multi processor
friendly (there is no
>> atomic "set bit"), and also compilers typically don't optimize well with
that (so before
>> applying this patch, I would test on other platforms than gcc linux x86).
is not true.
It's true not all CPUs have an atomic "set bit" operation.
Regards,
~Nuno Lucas
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