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

[Mathieu Desnoyers]

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 ?

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