From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <Ian.Campbell@citrix.com>
Subject: Re: [PATCH for-4.6] xenstored: log tdb message via
 xenstored's logging mechanisms
Date: Thu, 8 Jan 2015 13:10:38 +0000
Message-ID: <1420722638.19787.72.camel@citrix.com>
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To: Wei Liu <wei.liu2@citrix.com>
Cc: xen-devel@lists.xen.org, ian.jackson@eu.citrix.com, Philipp Hahn <hahn@univention.de>
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On Thu, 2015-01-08 at 13:04 +0000, Ian Campbell wrote:
> On Thu, 2015-01-08 at 12:57 +0000, Wei Liu wrote:
> > On Thu, Jan 08, 2015 at 12:33:29PM +0000, Ian Campbell wrote:
> > > ping.
> > > 
> > > On Mon, 2014-12-15 at 13:18 +0000, Ian Campbell wrote:
> > > > TDB provides us with a callback for this purpose. Use it in both
> > > > xenstored and xs_tdb_dump.
> > > > 
> > > > While at it make the existing log() macro tollerate memory failures.
> > > > 
> > > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> > > > ---
> > > >  tools/xenstore/xenstored_core.c |   39 +++++++++++++++++++++++++++++++++------
> > > >  tools/xenstore/xs_tdb_dump.c    |   12 +++++++++++-
> > > >  2 files changed, 44 insertions(+), 7 deletions(-)
> > > > 
> > > > diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
> > > > index 4eaff57..3fd9a20 100644
> > > > --- a/tools/xenstore/xenstored_core.c
> > > > +++ b/tools/xenstore/xenstored_core.c
> > > > @@ -89,9 +89,14 @@ static void check_store(void);
> > > >  #define log(...)							\
> > > >  	do {								\
> > > >  		char *s = talloc_asprintf(NULL, __VA_ARGS__);		\
> > > > -		trace("%s\n", s);					\
> > > > -		syslog(LOG_ERR, "%s",  s);				\
> > > > -		talloc_free(s);						\
> > > > +		if (s) {						\
> > > > +			trace("%s\n", s);				\
> > > > +			syslog(LOG_ERR, "%s",  s);			\
> > > > +			talloc_free(s);					\
> > > > +		} else {						\
> > > > +			trace("talloc failure during logging\n");	\
> > > > +			syslog(LOG_ERR, "talloc failure during logging\n"); \
> > > > +		}							\
> > 
> > talloc_free can tolerate NULL pointer.
> 
> Good point, I'll fix.

Hrm, it tolerates but it does return failure (-1) instead of success in
that case.

Literally nowhere in our code base actually checks the return value from
talloc_free, but nonetheless given that I think it would prefer to keep
the talloc_free where it is and therefore only pass a valid pointer to
it.

Ian.