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> --- Notes: 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 | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index db5c658919ad..45142ebab9e2 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -391,16 +391,19 @@ 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]) { - /* 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; } + + /* 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; } /* GETRA is the true target of the return instruction that we'll execute, -- 2.7.3