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

[Mathieu Desnoyers]

On 2024-05-02 10:32, Michael Jeanson wrote:
> 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.

For the records, we also have a copy of this code in lttng-ust,
also under MIT license. So liburcu's copy is the only outlier
there.

Thanks,

Mathieu

> 
>> 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.
>>
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com