* [lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs
@ 2024-05-01 23:42 Benjamin Marzinski via lttng-dev
2024-05-02 13:54 ` Mathieu Desnoyers via lttng-dev
0 siblings, 1 reply; 4+ messages in thread
From: Benjamin Marzinski via lttng-dev @ 2024-05-01 23:42 UTC (permalink / raw
To: lttng-dev
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.
Signed-off-by: Benjamin Marzinski <bmarzins@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.
--
2.44.0
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^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs
2024-05-01 23:42 [lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs Benjamin Marzinski via lttng-dev
@ 2024-05-02 13:54 ` Mathieu Desnoyers via lttng-dev
2024-05-02 14:32 ` Michael Jeanson via lttng-dev
0 siblings, 1 reply; 4+ messages in thread
From: Mathieu Desnoyers via lttng-dev @ 2024-05-02 13:54 UTC (permalink / raw
To: Benjamin Marzinski, lttng-dev, Michael Jeanson
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@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
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs
2024-05-02 13:54 ` Mathieu Desnoyers via lttng-dev
@ 2024-05-02 14:32 ` Michael Jeanson via lttng-dev
2024-05-02 14:34 ` Mathieu Desnoyers via lttng-dev
0 siblings, 1 reply; 4+ messages in thread
From: Michael Jeanson via lttng-dev @ 2024-05-02 14:32 UTC (permalink / raw
To: Mathieu Desnoyers, Benjamin Marzinski, lttng-dev
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@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.
>
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs
2024-05-02 14:32 ` Michael Jeanson via lttng-dev
@ 2024-05-02 14:34 ` Mathieu Desnoyers via lttng-dev
0 siblings, 0 replies; 4+ messages in thread
From: Mathieu Desnoyers via lttng-dev @ 2024-05-02 14:34 UTC (permalink / raw
To: Michael Jeanson, Benjamin Marzinski, lttng-dev
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@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
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lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
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2024-05-01 23:42 [lttng-dev] [PATCH urcu] fix: handle EINTR correctly in get_cpu_mask_from_sysfs Benjamin Marzinski via lttng-dev
2024-05-02 13:54 ` Mathieu Desnoyers via lttng-dev
2024-05-02 14:32 ` Michael Jeanson via lttng-dev
2024-05-02 14:34 ` Mathieu Desnoyers via lttng-dev
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