Hi Pranith,
Thank you for the hint, I will keep this in mind for the next version.
Regards,
alvise
On Tue, May 31, 2016 at 5:03 PM, Pranith Kumar <bobby.pr...@gmail.com> wrote:
> Hi Alvise,
>
> On Thu, May 26, 2016 at 12:35 PM, Alvise Rigo
> <a.r...@virtualopensystems.com> wrote:
>> Add tcg_exclusive_{lock,unlock}() functions that will be used for making
>> the emulation of LL and SC instructions thread safe.
>>
>> Signed-off-by: Alvise Rigo <a.r...@virtualopensystems.com>
>
> <snip>
>
>> +__thread bool cpu_have_exclusive_lock;
>> +QemuSpin cpu_exclusive_lock;
>> +inline void tcg_exclusive_lock(void)
>> +{
>> + if (!cpu_have_exclusive_lock) {
>> + qemu_spin_lock(&cpu_exclusive_lock);
>> + cpu_have_exclusive_lock = true;
>> + }
>> +}
>> +
>> +inline void tcg_exclusive_unlock(void)
>> +{
>> + if (cpu_have_exclusive_lock) {
>> + cpu_have_exclusive_lock = false;
>> + qemu_spin_unlock(&cpu_exclusive_lock);
>> + }
>> +}
>
> I think the unlock() here should have an assert if
> cpu_have_exclusive_lock is false. From what I can see, a thread should
> either take the exclusive lock or wait spinning for it in lock(). So
> unlock() should always see cpu_have_exclusive_lock as true. It is a
> good place to find locking bugs.
>
> --
> Pranith
