[ovs-dev] [threads 08/11] random: Make thread-safe.

Ben Pfaff blp at nicira.com
Tue Jun 25 05:03:36 UTC 2013


On Mon, Jun 24, 2013 at 03:50:45PM -0700, Ansis Atteka wrote:
> On Wed, Jun 19, 2013 at 1:17 PM, Ben Pfaff <blp at nicira.com> wrote:
> 
> > Signed-off-by: Ben Pfaff <blp at nicira.com>
> > ---
> >  lib/random.c |   26 +++++++++++++++++---------
> >  1 files changed, 17 insertions(+), 9 deletions(-)
> >
> > diff --git a/lib/random.c b/lib/random.c
> > index 45d428c..2572c1e 100644
> > --- a/lib/random.c
> > +++ b/lib/random.c
> > @@ -1,5 +1,5 @@
> >  /*
> > - * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc.
> > + * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
> >   *
> >   * Licensed under the Apache License, Version 2.0 (the "License");
> >   * you may not use this file except in compliance with the License.
> > @@ -22,6 +22,8 @@
> >  #include <sys/time.h>
> >
> >  #include "entropy.h"
> > +#include "hash.h"
> > +#include "ovs-thread.h"
> >  #include "timeval.h"
> >  #include "util.h"
> >
> > @@ -37,21 +39,25 @@
> >   * cryptographic-quality randomness. */
> >
> >  /* Current random state. */
> > -static uint32_t seed;
> > +DEFINE_PER_THREAD_DATA(uint32_t, seed, 0);
> >
> >  static uint32_t random_next(void);
> >
> >  void
> >  random_init(void)
> >  {
> > -    while (!seed) {
> >
> +    uint32_t *seedp = seed_get();
> 
> +    while (!*seedp) {
> >          struct timeval tv;
> >          uint32_t entropy;
> > +        pthread_t self;
> >
> >          xgettimeofday(&tv);
> >          get_entropy_or_die(&entropy, 4);
> >
> get_entropy() is not thread safe and that makes this function thread unsafe
> as well: get_entropy()->ovs_retval_to_string() uses "static char
> unknown[48]".

The patch titled "Replace all uses of strerror() by ovs_strerror(), for
thread safety."  should make ovs_retval_to_string() thread-safe, so I
believe that that is fixed earlier in the series.

Thanks,

Ben.



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