Did the patch apply? This issue still exist in xen-unstable(22364).
best regards
yang
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Christoph Egger
> Sent: Thursday, November 04, 2010 11:40 PM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Cc: Jackson; Stefano Stabellini
> Subject: Re: [Xen-devel][PATCH] xl create: endless loop
>
> On Wednesday 03 November 2010 17:12:47 Christoph Egger wrote:
> > On Thursday 21 October 2010 16:11:55 Stefano Stabellini wrote:
> > > On Tue, 19 Oct 2010, Christoph Egger wrote:
> > > > On Monday 18 October 2010 14:50:35 Christoph Egger wrote:
> > > > > Hi!
> > > > >
> > > > > I cannot start a guest with 'xl create' due to an endless loop
> > > > > in libxl.c, function libxl__get_free_memory_slack():
> > > > >
> > > > > There is this code snippet:
> > > > >
> > > > > retry:
> > > > > free_mem_slack_s = libxl__xs_read(gc, XBT_NULL,
> > > > > free_mem_slack_path); if (!free_mem_slack_s) {
> > > > > rc = libxl__fill_dom0_memory_info(gc, &target_memkb);
> > > > > if (rc < 0)
> > > > > return rc;
> > > > > goto retry;
> > > > > } else {
> > > > >
> > > > >
> > > > > libxl__xs_read() returns 0 and libxl__fill_dom0_memory_info()
> > > > > also returns 0. So there's a loop of retries.
> > > >
> > > > Attached patch fixes the endless loop.
> > > >
> > > > Signed-off-by: Christoph Egger <Christoph.Egger@xxxxxxx>
> > >
> > > thanks for the patch but this cannot possibly be the right fix:
> > >
> > >
> > > diff -r 9d8d6b93114e tools/libxl/libxl.c
> > > --- a/tools/libxl/libxl.c Mon Oct 18 15:24:39 2010 +0200
> > > +++ b/tools/libxl/libxl.c Tue Oct 19 10:29:00 2010 +0200
> > > @@ -2836,7 +2836,7 @@ retry:
> > > free_mem_slack_s = libxl__xs_read(gc, XBT_NULL,
> > > free_mem_slack_path); if (!free_mem_slack_s) {
> > > rc = libxl__fill_dom0_memory_info(gc, &target_memkb);
> > > - if (rc < 0)
> > > + if (rc <= 0)
> > > return rc;
> > > goto retry;
> > > } else {
> > >
> > > the idea is that libxl__fill_dom0_memory_info should fill the
> > > missing informations in xenstore so that we can go ahead and try to
> > > read them again and the second time should be successful.
> > > Libxl__fill_dom0_memory_info returns 0 on success, so it is correct
> > > to goto retry in that case.
> > >
> > > The bug must be in libxl__fill_dom0_memory_info that doesn't return
> > > error when it should.
> > > Does the appended patch works for you?
> > >
> > > ---
> > >
> > > diff -r 00b92112b055 tools/libxl/libxl.c
> > > --- a/tools/libxl/libxl.c Wed Oct 20 17:26:51 2010 +0100
> > > +++ b/tools/libxl/libxl.c Thu Oct 21 15:08:29 2010 +0100
> > > @@ -2793,11 +2793,11 @@ retry_transaction:
> > >
> > > rc = libxl_domain_info(ctx, &info, 0);
> > > if (rc < 0)
> > > - return rc;
> > > + goto out;
> > >
> > > rc = libxl_get_physinfo(ctx, &physinfo);
> > > if (rc < 0)
> > > - return rc;
> > > + goto out;
> > >
> > > libxl__xs_write(gc, t, target_path, "%"PRIu32,
> > > (uint32_t) info.current_memkb); @@ -2816,9 +2816,12
> @@
> > > retry_transaction:
> > > rc = 0;
> > >
> > > out:
> > > - if (!xs_transaction_end(ctx->xsh, t, 0))
> > > + if (!xs_transaction_end(ctx->xsh, t, 0)) {
> > > if (errno == EAGAIN)
> > > goto retry_transaction;
> > > + else
> > > + rc = ERROR_FAIL;
> > > + }
> > >
> > >
> > > return rc;
> >
> > No, this patch has no effect for me.
> > In libxl__fill_dom0_memory_info(), the code path goes that way:
> >
> > t = xs_transaction_start(ctx->xsh);
> >
> > target = libxl__xs_read(gc, t, target_path);
> > if (target) { <-- target contains "5"
> > *target_memkb = strtoul(target, &endptr, 10);
> > if (*endptr != '\0') { <-- *endptr contains '\0'
> > LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
> > "invalid memory target %s from %s\n", target,
> > target_path);
> > rc = ERROR_FAIL;
> > goto out;
> > }
> > rc = 0;
> > goto out; <-- take this jump with rc being 0
> > }
> >
>
> A slightly modified version works.
>
> Signed-off-by: Mark Langsdorf <Mark.Langsdorf@xxxxxxx>
> Signed-off-by: Christoph Egger <Christoph.Egger@xxxxxxx>
>
>
>
>
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