Re: [Valgrind-users] SfMayBlock with fuse-compatible

[Ivo R. <iv...@iv...>]

2016-12-08 11:28 GMT+01:00 Radoslaw Kujawa <ku...@9l...>:

>
> W dniu 08.12.2016 o 11:12, Ivo Raisr pisze:
>
>
>
> 2016-12-07 13:54 GMT+01:00 Radoslaw Kujawa <ku...@9l...>:
>
>> Hi Ivo,
>>
>> here is the log that appeared when we switched on trace-syscalls:
>>
>> SYSCALL[28094,1](89) sys_readlink ( 0x374581b667(/proc/self/exe),
>> 0xffeffec10, 4096 ) --> [pre-success] Success(0x52)
>> valgrind: m_syswrap/syswrap-main.c:1938 (vgPlain_client_syscall):
>> Assertion '0 == (sci->flags & ~(SfPollAfter | SfYieldAfter |
>> SfNoWriteResult))' failed.
>>
>
> Hi Radek,
>
> Thanks to the log you provided, I was able to quickly analyse the
> situation and get to the root cause.
> Pre-syscall wrapper for sys_readlink in syswrap-generic.c sets SfMayBlock
> unconditionally (via FUSE_COMPATIBLE_MAY_BLOCK)
> in the anticipation that the subsequent real syscall may block.
> However in some cases, such as when operating on /proc/self/exe, the
> wrapper calls the real syscall
> itself and therefore SfMayBlock should not have been set.
>
> If you are able to compile Valgrind from sources, I can prepare a small
> patch for you to test.
> Unfortunately I don't have an environment to test with FUSE for you.
> I.
>
>
> Yes, we can recompile Valgrind. We will be grateful if you prepare a patch
> for us.
> If it occurs that this patch resolves the problem, do you think we should
> report it as a bug via bugzilla?
>


Please find attached a patch. File a bug anyway and report your findings.
I.