[lxc-devel] [PATCH] fix multithreaded create()
Dwight Engen
dwight.engen at oracle.com
Tue Nov 12 20:31:34 UTC 2013
On Tue, 12 Nov 2013 14:35:58 -0500
S.Çağlar Onur <caglar at 10ur.org> wrote:
> On Tue, Nov 12, 2013 at 2:04 PM, Dwight Engen
> <dwight.engen at oracle.com> wrote:
> > We were calling save_config() twice within the create() flow, each
> > from a different process. Depending on order of scheduling,
> > sometimes the data from the first save_config() (which was just the
> > stuff from LXC_DEFAULT_CONFIG) would overwrite the config we wanted
> > (the full config), causing a truncated config file which would then
> > cause lxc to segfault once it read it back in because no
> > rootfs.path was set.
> >
> > This fixes it by only calling save_config() once in the create()
> > flow. A rejected alternative was to call fsync(fileno(fout)) before
> > the fclose in save_config.
> >
> > Signed-off-by: Dwight Engen <dwight.engen at oracle.com>
>
> Great news; This solved the concurrent create problems for me
> Bad news; I started to observe destroy() failures (see below)
Hmm, you are testing through the go binding correct? I ran these two
without error:
./src/tests/lxc-test-concurrent -i 200 -j 8 create,destroy
./src/tests/lxc-test-concurrent -i 100 -j 8
I wonder if lxc-test-concurrent will fail for you?
> [caglar at qp:~/go/src/github.com/caglar10ur/lxc/examples] sudo
> ./concurrent_stress -iteration=100 -count=10
> lxc_container: Error destroying rootfs for 5
> 2013/11/12 14:31:43 [ERROR] ERROR: destroying the
> container "5" failed
> 2013/11/12 14:31:43 [ERROR] ERROR: container "5"
> already defined
> lxc_container: Error destroying rootfs for 1
> 2013/11/12 14:32:10 [ERROR] ERROR: destroying the
> container "1" failed
> 2013/11/12 14:32:10 [ERROR] ERROR: container "1"
> already defined
> lxc_container: Error destroying rootfs for 1
> 2013/11/12 14:32:25 [ERROR] ERROR: destroying the
> container "1" failed
> 2013/11/12 14:32:25 [ERROR] ERROR: container "1"
> already defined
> lxc_container: Error destroying rootfs for 7
> 2013/11/12 14:32:30 [ERROR] ERROR: destroying the
> container "7" failed
> 2013/11/12 14:32:30 [ERROR] ERROR: container "7"
> already defined
> lxc_container: Error destroying rootfs for 4
> 2013/11/12 14:33:25 [ERROR] ERROR: destroying the
> container "4" failed
> 2013/11/12 14:33:25 [ERROR] ERROR: container "4"
> already defined
> lxc_container: Error destroying rootfs for 0
> 2013/11/12 14:33:40 [ERROR] ERROR: destroying the
> container "0" failed
> 2013/11/12 14:33:40 [ERROR] ERROR: container "0"
> already defined
> lxc_container: Error destroying rootfs for 0
> 2013/11/12 14:33:45 [ERROR] ERROR: destroying the
> container "0" failed
> 2013/11/12 14:33:45 [ERROR] ERROR: container "0"
> already defined
> lxc_container: Error destroying rootfs for 8
> 2013/11/12 14:33:55 [ERROR] ERROR: destroying the
> container "8" failed
> 2013/11/12 14:33:55 [ERROR] ERROR: container "8"
> already defined
> lxc_container: Error destroying rootfs for 2
> 2013/11/12 14:34:40 [ERROR] ERROR: destroying the
> container "2" failed
> 2013/11/12 14:34:40 [ERROR] ERROR: container "2"
> already defined
> lxc_container: Error destroying rootfs for 1
> 2013/11/12 14:34:45 [ERROR] ERROR: destroying the
> container "1" failed
> 2013/11/12 14:34:45 [ERROR] ERROR: container "1"
> already defined
> lxc_container: Error destroying rootfs for 9
> 2013/11/12 14:35:00 [ERROR] ERROR: destroying the
> container "9" failed
> 2013/11/12 14:35:01 [ERROR] ERROR: container "9"
> already defined
> [caglar at qp:~/go/src/github.com/caglar10ur/lxc/examples]
>
> but since the original problem is gone now
>
> Acked-by: S.Çağlar Onur <caglar at 10ur.org>
>
> > ---
> > src/lxc/lxccontainer.c | 20 ++++++++++++--------
> > 1 file changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> > index c7b2f5e..05ca643 100644
> > --- a/src/lxc/lxccontainer.c
> > +++ b/src/lxc/lxccontainer.c
> > @@ -1192,16 +1192,19 @@ static bool lxcapi_create(struct
> > lxc_container *c, const char *t, if (lxcapi_is_defined(c) &&
> > c->lxc_conf && c->lxc_conf->rootfs.path &&
> > access(c->lxc_conf->rootfs.path, F_OK) == 0 && tpath)
> > { ERROR("Container %s:%s already exists", c->config_path, c->name);
> > - free(tpath);
> > - return false;
> > + goto free_tpath;
> > }
> >
> > - /* Save the loaded configuration to disk */
> > - if (!c->save_config(c, NULL)) {
> > - ERROR("failed to save starting configuration for
> > %s\n", c->name);
> > - goto out;
> > + if (!c->lxc_conf) {
> > + if (!c->load_config(c, LXC_DEFAULT_CONFIG)) {
> > + ERROR("Error loading default configuration
> > file %s\n", LXC_DEFAULT_CONFIG);
> > + goto free_tpath;
> > + }
> > }
> >
> > + if (!create_container_dir(c))
> > + goto free_tpath;
> > +
> > /*
> > * either template or rootfs.path should be set.
> > * if both template and rootfs.path are set, template is
> > setup as rootfs.path. @@ -1290,10 +1293,11 @@ out_unlock:
> > if (partial_fd >= 0)
> > remove_partial(c, partial_fd);
> > out:
> > - if (tpath)
> > - free(tpath);
> > if (!ret && c)
> > lxcapi_destroy(c);
> > +free_tpath:
> > + if (tpath)
> > + free(tpath);
> > return ret;
> > }
> >
> > --
> > 1.8.3.1
> >
> >
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