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

[Radoslaw K. <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... 
> <mailto: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?

Radek