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
}
Christoph
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