Commit 9962c478 authored by Sergey Fedorov's avatar Sergey Fedorov Committed by Richard Henderson
Browse files

tcg: Clarify thread safety check in tb_add_jump() 



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: default avatarSergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: default avatarSergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: default avatarRichard Henderson <rth@twiddle.net>
parent 901bc3de

include/exec/exec-all.h

+16 −13
Original line number Diff line number Diff line
@@ -372,13 +372,17 @@ 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]) {

    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);
@@ -386,7 +390,6 @@ static inline void tb_add_jump(TranslationBlock *tb, int n, 
    tb->jmp_list_next[n] = tb_next->jmp_list_first;

    tb_next->jmp_list_first = (uintptr_t)tb | n;

}

}



/* GETRA is the true target of the return instruction that we'll execute,

   defined here for simplicity of defining the follow-up macros.  */