Re: [Qemu-devel] [PATCH] translate-all: Enable locking debug in a debug build

["Alex Bennée" <alex.bennee@linaro.org>]

Pranith Kumar <bobby.prani@gmail.com> writes:

> Unconditionally enable locking checks in debug builds so that we get
> wider testing. Using tcg_debug_assert() allows us to remove
> DEBUG_LOCKING define.

Interesting. The other option would be to add a debug build to
.travis.yml that define this (and others) with -DFOO_DEBUG.

>
> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
> ---
>  translate-all.c | 50 +++++++++++++++++---------------------------------
>  1 file changed, 17 insertions(+), 33 deletions(-)
>
> diff --git a/translate-all.c b/translate-all.c
> index cf828aa..a03f323 100644
> --- a/translate-all.c
> +++ b/translate-all.c
> @@ -60,7 +60,6 @@
>
>  /* #define DEBUG_TB_INVALIDATE */
>  /* #define DEBUG_TB_FLUSH */
> -/* #define DEBUG_LOCKING */
>  /* make various TB consistency checks */
>  /* #define DEBUG_TB_CHECK */

So if we are enabling this for tcg_debug builds why not the other cases?

>
> @@ -75,23 +74,13 @@
>   * access to the memory related structures are protected with the
>   * mmap_lock.
>   */
> -#ifdef DEBUG_LOCKING
> -#define DEBUG_MEM_LOCKS 1
> -#else
> -#define DEBUG_MEM_LOCKS 0
> -#endif
> -

In retrospect I should probably of had a comment in here about the roll
of tb_lock in CONFIG_SOFTMMU versus the mmap_lock.

>  #ifdef CONFIG_SOFTMMU
>  #define assert_memory_lock() do {           \
> -        if (DEBUG_MEM_LOCKS) {              \
> -            g_assert(have_tb_lock);         \
> -        }                                   \
> +        tcg_debug_assert(have_tb_lock);     \
>      } while (0)
>  #else
>  #define assert_memory_lock() do {               \
> -        if (DEBUG_MEM_LOCKS) {                  \
> -            g_assert(have_mmap_lock());         \
> -        }                                       \
> +        tcg_debug_assert(have_mmap_lock());     \
>      } while (0)
>  #endif
>
> @@ -172,16 +161,24 @@ static void page_table_config_init(void)
>      assert(v_l2_levels >= 0);
>  }
>
> +#define assert_tb_locked() do {             \
> +        tcg_debug_assert(have_tb_lock);     \
> +    } while (0)
> +
> +#define assert_tb_unlocked() do {           \
> +        tcg_debug_assert(!have_tb_lock);    \
> +    } while (0)
> +

I'm not sure we need all this multi-line stuff for a simple
substitution? Richard?

>  void tb_lock(void)
>  {
> -    assert(!have_tb_lock);
> +    assert_tb_unlocked();

Hmm why introduce a helper for exactly one use?

>      qemu_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
>      have_tb_lock++;
>  }
>
>  void tb_unlock(void)
>  {
> -    assert(have_tb_lock);
> +    assert_tb_locked();
>      have_tb_lock--;
>      qemu_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
>  }
> @@ -194,19 +191,6 @@ void tb_lock_reset(void)
>      }
>  }
>
> -#ifdef DEBUG_LOCKING
> -#define DEBUG_TB_LOCKS 1
> -#else
> -#define DEBUG_TB_LOCKS 0
> -#endif
> -
> -#define assert_tb_lock() do {               \
> -        if (DEBUG_TB_LOCKS) {               \
> -            g_assert(have_tb_lock);         \
> -        }                                   \
> -    } while (0)
> -
> -
>  static TranslationBlock *tb_find_pc(uintptr_t tc_ptr);
>
>  void cpu_gen_init(void)
> @@ -840,7 +824,7 @@ static TranslationBlock *tb_alloc(target_ulong pc)
>  {
>      TranslationBlock *tb;
>
> -    assert_tb_lock();
> +    assert_tb_locked();
>
>      if (tcg_ctx.tb_ctx.nb_tbs >= tcg_ctx.code_gen_max_blocks) {
>          return NULL;
> @@ -855,7 +839,7 @@ static TranslationBlock *tb_alloc(target_ulong pc)
>  /* Called with tb_lock held.  */
>  void tb_free(TranslationBlock *tb)
>  {
> -    assert_tb_lock();
> +    assert_tb_locked();
>
>      /* In practice this is mostly used for single use temporary TB
>         Ignore the hard cases and just back up if this TB happens to
> @@ -1097,7 +1081,7 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
>      uint32_t h;
>      tb_page_addr_t phys_pc;
>
> -    assert_tb_lock();
> +    assert_tb_locked();
>
>      atomic_set(&tb->invalid, true);
>
> @@ -1412,7 +1396,7 @@ static void tb_invalidate_phys_range_1(tb_page_addr_t start, tb_page_addr_t end)
>  #ifdef CONFIG_SOFTMMU
>  void tb_invalidate_phys_range(tb_page_addr_t start, tb_page_addr_t end)
>  {
> -    assert_tb_lock();
> +    assert_tb_locked();
>      tb_invalidate_phys_range_1(start, end);
>  }
>  #else
> @@ -1455,7 +1439,7 @@ void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
>  #endif /* TARGET_HAS_PRECISE_SMC */
>
>      assert_memory_lock();
> -    assert_tb_lock();
> +    assert_tb_locked();
>
>      p = page_find(start >> TARGET_PAGE_BITS);
>      if (!p) {


--
Alex Bennée