[PING] Race condition in initialisation of stdio standard streams

Sean Harte sean.harte@linux.intel.com
Mon Apr 9 19:08:00 GMT 2012

Has anyone checked below issue?


> Hi,
> I believe there is a race condition in the initialisation and use of
> recursive locks used in the _stdin, _stdout, and _stderr files. In
> __sinit() in findfp.c, the __sdidinit field is set to 1 before the actual
> initialisation is done. Other threads could read this field (e.g. by using
> the CHECK_INIT() macro in local.h) and proceed to access one of the
> standard files before it is initialised. This can result in unwanted
> behaviour due to calling _flockfile() before the lock is setup.
> Such behaviour can be reproduced by simultaneously calling a function that
> will result in initialisation of a standard file in multiple threads (on a
> SMP system). For example if _stdout is not yet initialised and printf() is
> called on multiple threads simultaneously, sometimes only one thread will
> print output.
> This behaviour can be fixed by moving the setting of __sdidinit in
> __sinit() to after the standard files are initialised, putting it
> immediately before the call to __sinit_lock_release(). Preferably there
> should be a memory barrier before setting __sdidinit also.
> Regards,
> Seán Harte

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