Re: [RFC v5 034/126] MIPS Machines: introduce ERRP_AUTO_PROPAGATE

[Vladimir Sementsov-Ogievskiy]

12.10.2019 9:22, Philippe Mathieu-Daudé wrote:
> Hi Vladimir,
> 
> On 10/11/19 6:04 PM, Vladimir Sementsov-Ogievskiy wrote:
>> If we want to add some info to errp (by error_prepend() or
>> error_append_hint()), we must use the ERRP_AUTO_PROPAGATE macro.
>> Otherwise, this info will not be added when errp == &fatal_err
>> (the program will exit prior to the error_append_hint() or
>> error_prepend() call).  Fix such cases.
>>
>> If we want to check error after errp-function call, we need to
>> introduce local_err and than propagate it to errp. Instead, use
>> ERRP_AUTO_PROPAGATE macro, benefits are:
>> 1. No need of explicit error_propagate call
>> 2. No need of explicit local_err variable: use errp directly
>> 3. ERRP_AUTO_PROPAGATE leaves errp as is if it's not NULL or
>>     &error_fatel, this means that we don't break error_abort
>>     (we'll abort on error_set, not on error_propagate)
>>
>> This commit (together with its neighbors) was generated by
>>
>> for f in $(git grep -l errp \*.[ch]); do \
>>      spatch --sp-file scripts/coccinelle/auto-propagated-errp.cocci \
>>      --macro-file scripts/cocci-macro-file.h --in-place --no-show-diff $f; \
>> done;
>>
>> then fix a bit of compilation problems: coccinelle for some reason
>> leaves several
>> f() {
>>      ...
>>      goto out;
>>      ...
>>      out:
>> }
>> patterns, with "out:" at function end.
>>
>> then
>> ./python/commit-per-subsystem.py MAINTAINERS "$(< auto-msg)"
>>
>> (auto-msg was a file with this commit message)
>>
>> Still, for backporting it may be more comfortable to use only the first
>> command and then do one huge commit.
>>
>> Reported-by: Kevin Wolf <address@hidden>
>> Reported-by: Greg Kurz <address@hidden>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>> ---
>>   hw/core/loader-fit.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/hw/core/loader-fit.c b/hw/core/loader-fit.c
>> index 3ee9fb2f2e..84f35a1fe2 100644
>> --- a/hw/core/loader-fit.c
>> +++ b/hw/core/loader-fit.c
>> @@ -120,6 +120,7 @@ static int fit_load_kernel(const struct fit_loader *ldr, 
>> const void *itb,
>>                              int cfg, void *opaque, hwaddr *pend,
>>                              Error **errp)
>>   {
>> +    ERRP_AUTO_PROPAGATE();
> 
> This certainly looks odd and took me some time to figure it out.
> 
> Per include/qapi/error.h:
> 
> /*
>   * ERRP_AUTO_PROPAGATE
>   *
>   * This macro is created to be the first line of a function with Error *errp
>   * OUT parameter. It's needed only in cases where we want to use 
> rror_prepend,
>   * error_append_hint or dereference *errp. It's still safe (but useless) in
>   * other cases.
> 
> This function indeed uses error_prepend():
> 
>      load_data = data = fit_load_image_alloc(itb, name, &img_off, &sz, errp);
>      if (!data) {
>          error_prepend(errp, "unable to load kernel image from FIT: ");
>          return -EINVAL;
>      }
> 
>      err = fit_image_addr(itb, img_off, "load", &load_addr, errp);
>      if (err) {
>          error_prepend(errp, "unable to read kernel load address from FIT: ");
>          ret = err;
>          goto out;
>      }
> 
>      err = fit_image_addr(itb, img_off, "entry", &entry_addr, errp);
>      if (err) {
>          error_prepend(errp, "unable to read kernel entry address from FIT: 
> ");
>          ret = err;
>          goto out;
>      }
> 
> Generating the patch with more lines context would have help a bit.
> 
> Can you add a line about error_prepend() in the commit description?

Hmm, its already in it: "If we want to add some info to errp (by 
error_prepend() ...".
But better suggestions for commit message wording are welcome, of course.

> 
>>       const char *name;
>>       const void *data;
>>       const void *load_data;
>> @@ -178,6 +179,7 @@ static int fit_load_fdt(const struct fit_loader *ldr, 
>> const void *itb,
>>                           int cfg, void *opaque, const void *match_data,
>>                           hwaddr kernel_end, Error **errp)
>>   {
>> +    ERRP_AUTO_PROPAGATE();
>>       const char *name;
>>       const void *data;
>>       const void *load_data;
>>
> 
> Ditto:
> 
>      load_data = data = fit_load_image_alloc(itb, name, &img_off, &sz, errp);
>      if (!data) {
>          error_prepend(errp, "unable to load FDT image from FIT: ");
>          return -EINVAL;
>      }
> 
>      err = fit_image_addr(itb, img_off, "load", &load_addr, errp);
>      if (err == -ENOENT) {
>          load_addr = ROUND_UP(kernel_end, 64 * KiB) + (10 * MiB);
>          error_free(*errp);
>      } else if (err) {
>          error_prepend(errp, "unable to read FDT load address from FIT: ");
>          ret = err;
>          goto out;
>      }
> 
> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>


-- 
Best regards,
Vladimir