[lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs

[Michael Jeanson]

On 2024-05-02 09:54, Mathieu Desnoyers wrote:
> On 2024-05-01 19:42, Benjamin Marzinski via lttng-dev wrote:
>> If the read() in get_cpu_mask_from_sysfs() fails with EINTR, the code is
>> supposed to retry, but the while loop condition has (bytes_read > 0),
>> which is false when read() fails with EINTR. The result is that the code
>> exits the loop, having only read part of the string.
>>
>> Use (bytes_read != 0) in the while loop condition instead, since the
>> (bytes_read < 0) case is already handled in the loop.
> 
> Thanks for the fix ! It is indeed the right thing to do.
> 
> I would like to integrate this fix into the librseq and libside
> projects as well though, but I notice the the copy in liburcu
> is LGPLv2.1 whereas the copy in librseq and libside are
> MIT.
> 
> Michael, should we first relicense the liburcu src/compat-smp.h
> implementation to MIT so it matches the license of the copies
> in librseq and libside ?

Sure, please go ahead.

> Thanks,
> 
> Mathieu
> 
>>
>> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
>> ---
>>   src/compat-smp.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/compat-smp.h b/src/compat-smp.h
>> index 31fa979..075a332 100644
>> --- a/src/compat-smp.h
>> +++ b/src/compat-smp.h
>> @@ -164,7 +164,7 @@ static inline int get_cpu_mask_from_sysfs(char *buf, 
>> size_t max_bytes, const cha
>>           total_bytes_read += bytes_read;
>>           assert(total_bytes_read <= max_bytes);
>> -    } while (max_bytes > total_bytes_read && bytes_read > 0);
>> +    } while (max_bytes > total_bytes_read && bytes_read != 0);
>>       /*
>>        * Make sure the mask read is a null terminated string.
>