Re: [Xen-devel] [PATCH for-4.6] xenstored: log tdb message via xenstored's logging mechanisms

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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@xxxxxxxxxx>
> > > ---
> > >  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. I think I'll also change the message to more
clearly indicate an allocation failure, since that is what has actually
happened.

> > >   } while (0)
> > >  
> [...]
> > > +         tdb_ctx = tdb_open_ex(tdbname, 0, tdb_flags, O_RDWR, 0,
> > > +                               &tdb_logger, NULL);
> [...]
> > > +         tdb_ctx = tdb_open_ex(tdbname, 7919, tdb_flags, O_RDWR|O_CREAT,
> > > +                               0640, &tdb_logger, NULL);
> [...]
> > > + tdb = tdb_open_ex(talloc_strdup(NULL, argv[1]), 0, 0, O_RDONLY, 0,
> > > +                   tdb_logger, NULL);
> 
> Should be &tdb_logger?

tdb_logger is a function, so it's not strictly required, but it is good
form (and a hint to the reader) plus inconsistent with the others, so
I'll change.

Ian.



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