On 19/04/16 14:01, Alex Bennée wrote:
> Sergey Fedorov <sergey.fedo...@linaro.org> writes:
>
>> From: Sergey Fedorov <serge.f...@gmail.com>
>>
>> The check is to make sure that another thread hasn't already done the
>> same while we were outside of tb_lock. Mention this in a comment.
>>
>> Signed-off-by: Sergey Fedorov <serge.f...@gmail.com>
>> Signed-off-by: Sergey Fedorov <sergey.fedo...@linaro.org>
>> ---
>>
>> Changes in v2:
>> * Typo fixed in the commit title
>> * Complete rewrite of the commit body and the patch based on Paolo's
>> comments
>>
>> include/exec/exec-all.h | 31 +++++++++++++++++--------------
>> 1 file changed, 17 insertions(+), 14 deletions(-)
>>
>> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
>> index b055716ed690..8e81ef5fb2c2 100644
>> --- a/include/exec/exec-all.h
>> +++ b/include/exec/exec-all.h
>> @@ -391,21 +391,24 @@ static inline void tb_set_jmp_target(TranslationBlock
>> *tb,
>> static inline void tb_add_jump(TranslationBlock *tb, int n,
>> TranslationBlock *tb_next)
>> {
>> - /* NOTE: this test is only needed for thread safety */
>> - if (!tb->jmp_list_next[n]) {
>> - qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
>> - "Linking TBs %p [" TARGET_FMT_lx
>> - "] index %d -> %p [" TARGET_FMT_lx "]\n",
>> - tb->tc_ptr, tb->pc, n,
>> - tb_next->tc_ptr, tb_next->pc);
>> - /* patch the native jump address */
>> - tb_set_jmp_target(tb, n, (uintptr_t)tb_next->tc_ptr);
>> -
>> - /* add in TB jmp circular list */
>> - tb->jmp_list_next[n] = tb_next->jmp_list_first;
>> - assert(((uintptr_t)tb & 3) == 0);
>> - tb_next->jmp_list_first = (uintptr_t)tb | n;
>> + if (tb->jmp_list_next[n]) {
>> + /* Another thread has already done this while we were
>> + * outside of the lock; nothing to do in this case */
>> + return;
>> }
>> + qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
>> + "Linking TBs %p [" TARGET_FMT_lx
>> + "] index %d -> %p [" TARGET_FMT_lx "]\n",
>> + tb->tc_ptr, tb->pc, n,
>> + tb_next->tc_ptr, tb_next->pc);
>> +
>> + /* patch the native jump address */
>> + tb_set_jmp_target(tb, n, (uintptr_t)tb_next->tc_ptr);
>> +
>> + /* add in TB jmp circular list */
>> + tb->jmp_list_next[n] = tb_next->jmp_list_first;
>> + assert(((uintptr_t)tb & 3) == 0);
> I think this assert can be dropped. The only call explicitly masks with
> TB_EXIT_MASK (which would be a better choice than the number 3 anyway)
> so something really strange would have had to happen in the intervening
> few lines.
What about the same assert in tb_gen_code()?
Kind regards,
Sergey
>
> Otherwise:
>
> Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
>
>> + tb_next->jmp_list_first = (uintptr_t)tb | n;
>> }
>>
>> /* GETRA is the true target of the return instruction that we'll execute,
>
