* [PATCH] libxl: trigger attach events for devices attached before xl devd startup @ 2016-07-10 17:35 Marek Marczykowski-Górecki 2016-07-11 8:31 ` Roger Pau Monné 0 siblings, 1 reply; 12+ messages in thread From: Marek Marczykowski-Górecki @ 2016-07-10 17:35 UTC (permalink / raw) To: xen-devel; +Cc: Wei Liu, Ian Jackson, Marek Marczykowski-Górecki When this daemon is started after creating backend device, that device will not be configured. Racy situation: 1. driver domain is started 2. frontend domain is started (just after kicking driver domain off) 3. device in frontend domain is connected to the backend (as specified in frontend domain configuration) 4. xl devd is started in driver domain End result is that backend device in driver domain is not configured (like network interface is not enabled), so the device doesn't work. Fix this by artifically triggering events for devices already present in xenstore before xl devd is started. Do this only after xenstore watch is already registered, and only for devices not already initialized (in XenbusStateInitWait state). Cc: Ian Jackson <ian.jackson@eu.citrix.com> Cc: Wei Liu <wei.liu2@citrix.com> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> --- tools/libxl/libxl.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c index 1c81239..99815a7 100644 --- a/tools/libxl/libxl.c +++ b/tools/libxl/libxl.c @@ -4743,8 +4743,16 @@ int libxl_device_events_handler(libxl_ctx *ctx, uint32_t domid; libxl__ddomain ddomain; char *be_path; + char **kinds = NULL, **domains = NULL, **devs = NULL; + const char *sstate; + char *state_path; + int state; + unsigned int nkinds, ndomains, ndevs; + int i, j, k; + xs_transaction_t t; ddomain.ao = ao; + FILLZERO(ddomain.watch); LIBXL_SLIST_INIT(&ddomain.guests); rc = libxl__get_domid(gc, &domid); @@ -4762,9 +4770,41 @@ int libxl_device_events_handler(libxl_ctx *ctx, be_path); if (rc) goto out; + rc = libxl__xs_transaction_start(gc, &t); + if (rc) goto out; + kinds = libxl__xs_directory(gc, t, be_path, &nkinds); + if (kinds) { + for (i = 0; i < nkinds; i++) { + domains = libxl__xs_directory(gc, t, + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); + if (!domains) + continue; + for (j = 0; j < ndomains; j++) { + devs = libxl__xs_directory(gc, t, + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); + if (!devs) + continue; + for (k = 0; k < ndevs; k++) { + state_path = GCSPRINTF("%s/%s/%s/%s/state", + be_path, kinds[i], domains[j], devs[k]); + rc = libxl__xs_read_checked(gc, t, state_path, &sstate); + if (rc) + continue; + state = atoi(sstate); + if (state == XenbusStateInitWait) + backend_watch_callback(egc, &ddomain.watch, + be_path, state_path); + } + } + } + } + + libxl__xs_transaction_abort(gc, &t); + return AO_INPROGRESS; out: + libxl__ev_xswatch_deregister(gc, &ddomain.watch); return AO_CREATE_FAIL(rc); } -- 2.5.5 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH] libxl: trigger attach events for devices attached before xl devd startup 2016-07-10 17:35 [PATCH] libxl: trigger attach events for devices attached before xl devd startup Marek Marczykowski-Górecki @ 2016-07-11 8:31 ` Roger Pau Monné 2016-07-11 8:56 ` Marek Marczykowski-Górecki 0 siblings, 1 reply; 12+ messages in thread From: Roger Pau Monné @ 2016-07-11 8:31 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Ian Jackson, Wei Liu, xen-devel On Sun, Jul 10, 2016 at 07:35:47PM +0200, Marek Marczykowski-Górecki wrote: > When this daemon is started after creating backend device, that device > will not be configured. > > Racy situation: > 1. driver domain is started > 2. frontend domain is started (just after kicking driver domain off) > 3. device in frontend domain is connected to the backend (as specified > in frontend domain configuration) > 4. xl devd is started in driver domain > > End result is that backend device in driver domain is not configured > (like network interface is not enabled), so the device doesn't work. > > Fix this by artifically triggering events for devices already present in > xenstore before xl devd is started. Do this only after xenstore watch is > already registered, and only for devices not already initialized (in > XenbusStateInitWait state). Thanks! > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > Cc: Wei Liu <wei.liu2@citrix.com> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > --- > tools/libxl/libxl.c | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c > index 1c81239..99815a7 100644 > --- a/tools/libxl/libxl.c > +++ b/tools/libxl/libxl.c > @@ -4743,8 +4743,16 @@ int libxl_device_events_handler(libxl_ctx *ctx, > uint32_t domid; > libxl__ddomain ddomain; > char *be_path; > + char **kinds = NULL, **domains = NULL, **devs = NULL; > + const char *sstate; > + char *state_path; > + int state; > + unsigned int nkinds, ndomains, ndevs; > + int i, j, k; > + xs_transaction_t t; > > ddomain.ao = ao; > + FILLZERO(ddomain.watch); Is this a different bugfix or stray change? > LIBXL_SLIST_INIT(&ddomain.guests); > > rc = libxl__get_domid(gc, &domid); > @@ -4762,9 +4770,41 @@ int libxl_device_events_handler(libxl_ctx *ctx, > be_path); > if (rc) goto out; > > + rc = libxl__xs_transaction_start(gc, &t); > + if (rc) goto out; Why do you need to start a transaction here if you end up aborting it when finished? > + kinds = libxl__xs_directory(gc, t, be_path, &nkinds); > + if (kinds) { > + for (i = 0; i < nkinds; i++) { > + domains = libxl__xs_directory(gc, t, > + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); > + if (!domains) > + continue; > + for (j = 0; j < ndomains; j++) { > + devs = libxl__xs_directory(gc, t, > + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); > + if (!devs) > + continue; > + for (k = 0; k < ndevs; k++) { > + state_path = GCSPRINTF("%s/%s/%s/%s/state", > + be_path, kinds[i], domains[j], devs[k]); > + rc = libxl__xs_read_checked(gc, t, state_path, &sstate); > + if (rc) > + continue; > + state = atoi(sstate); > + if (state == XenbusStateInitWait) > + backend_watch_callback(egc, &ddomain.watch, > + be_path, state_path); > + } > + } > + } > + } > + > + libxl__xs_transaction_abort(gc, &t); > + > return AO_INPROGRESS; > > out: > + libxl__ev_xswatch_deregister(gc, &ddomain.watch); This seems to be part of a different bugfix also. Roger. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 8:31 ` Roger Pau Monné @ 2016-07-11 8:56 ` Marek Marczykowski-Górecki 2016-07-11 9:43 ` Roger Pau Monné 0 siblings, 1 reply; 12+ messages in thread From: Marek Marczykowski-Górecki @ 2016-07-11 8:56 UTC (permalink / raw) To: Roger Pau Monné; +Cc: Ian Jackson, Wei Liu, xen-devel [-- Attachment #1.1: Type: text/plain, Size: 4993 bytes --] On Mon, Jul 11, 2016 at 10:31:17AM +0200, Roger Pau Monné wrote: > On Sun, Jul 10, 2016 at 07:35:47PM +0200, Marek Marczykowski-Górecki wrote: > > When this daemon is started after creating backend device, that device > > will not be configured. > > > > Racy situation: > > 1. driver domain is started > > 2. frontend domain is started (just after kicking driver domain off) > > 3. device in frontend domain is connected to the backend (as specified > > in frontend domain configuration) > > 4. xl devd is started in driver domain > > > > End result is that backend device in driver domain is not configured > > (like network interface is not enabled), so the device doesn't work. > > > > Fix this by artifically triggering events for devices already present in > > xenstore before xl devd is started. Do this only after xenstore watch is > > already registered, and only for devices not already initialized (in > > XenbusStateInitWait state). > > Thanks! > > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > > Cc: Wei Liu <wei.liu2@citrix.com> > > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > > --- > > tools/libxl/libxl.c | 40 ++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 40 insertions(+) > > > > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c > > index 1c81239..99815a7 100644 > > --- a/tools/libxl/libxl.c > > +++ b/tools/libxl/libxl.c > > @@ -4743,8 +4743,16 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > uint32_t domid; > > libxl__ddomain ddomain; > > char *be_path; > > + char **kinds = NULL, **domains = NULL, **devs = NULL; > > + const char *sstate; > > + char *state_path; > > + int state; > > + unsigned int nkinds, ndomains, ndevs; > > + int i, j, k; > > + xs_transaction_t t; > > > > ddomain.ao = ao; > > + FILLZERO(ddomain.watch); > > Is this a different bugfix or stray change? To cleanly unregister watch and not do nothing if wasn't registered at all. If it isn't initialized, libxl__ev_xswatch_deregister call on not registered watch isn't harmless. > > LIBXL_SLIST_INIT(&ddomain.guests); > > > > rc = libxl__get_domid(gc, &domid); > > @@ -4762,9 +4770,41 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > be_path); > > if (rc) goto out; > > > > + rc = libxl__xs_transaction_start(gc, &t); > > + if (rc) goto out; > > Why do you need to start a transaction here if you end up aborting it when > finished? Mostly to ease error checking. Because below code does three level listing, I don't want to deal with races where some entry was removed between those calls, at least not here. Like this: xs_directory('backend/vif') -> 3, 4, 5 xs_directory('backend/vif/3') -> 0, 1 xs_read('backend/vif/3/0/state') -> ... xs_read('backend/vif/3/1/state') -> ... toolstack removes backend/vif/4 here xs_directory('backend/vif/4') -> fail Of course backend_watch_callback would fail anyway in such a case, which is ok. But having snapshot of xenstore during this multi-level listing looks like avoiding some corner cases during listing itself. > > + kinds = libxl__xs_directory(gc, t, be_path, &nkinds); > > + if (kinds) { > > + for (i = 0; i < nkinds; i++) { > > + domains = libxl__xs_directory(gc, t, > > + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); > > + if (!domains) > > + continue; > > + for (j = 0; j < ndomains; j++) { > > + devs = libxl__xs_directory(gc, t, > > + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); > > + if (!devs) > > + continue; > > + for (k = 0; k < ndevs; k++) { > > + state_path = GCSPRINTF("%s/%s/%s/%s/state", > > + be_path, kinds[i], domains[j], devs[k]); > > + rc = libxl__xs_read_checked(gc, t, state_path, &sstate); > > + if (rc) > > + continue; > > + state = atoi(sstate); > > + if (state == XenbusStateInitWait) > > + backend_watch_callback(egc, &ddomain.watch, > > + be_path, state_path); > > + } > > + } > > + } > > + } > > + > > + libxl__xs_transaction_abort(gc, &t); > > + > > return AO_INPROGRESS; > > > > out: > > + libxl__ev_xswatch_deregister(gc, &ddomain.watch); > > This seems to be part of a different bugfix also. No, this code previously wasn't reachable if xswatch was correctly registered. -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 473 bytes --] [-- Attachment #2: Type: text/plain, Size: 127 bytes --] _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 8:56 ` Marek Marczykowski-Górecki @ 2016-07-11 9:43 ` Roger Pau Monné 2016-07-11 9:49 ` Marek Marczykowski-Górecki 0 siblings, 1 reply; 12+ messages in thread From: Roger Pau Monné @ 2016-07-11 9:43 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Ian Jackson, Wei Liu, xen-devel On Mon, Jul 11, 2016 at 10:56:04AM +0200, Marek Marczykowski-Górecki wrote: > On Mon, Jul 11, 2016 at 10:31:17AM +0200, Roger Pau Monné wrote: > > On Sun, Jul 10, 2016 at 07:35:47PM +0200, Marek Marczykowski-Górecki wrote: > > > When this daemon is started after creating backend device, that device > > > will not be configured. > > > > > > Racy situation: > > > 1. driver domain is started > > > 2. frontend domain is started (just after kicking driver domain off) > > > 3. device in frontend domain is connected to the backend (as specified > > > in frontend domain configuration) > > > 4. xl devd is started in driver domain > > > > > > End result is that backend device in driver domain is not configured > > > (like network interface is not enabled), so the device doesn't work. > > > > > > Fix this by artifically triggering events for devices already present in > > > xenstore before xl devd is started. Do this only after xenstore watch is > > > already registered, and only for devices not already initialized (in > > > XenbusStateInitWait state). > > > > Thanks! > > > > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > > > Cc: Wei Liu <wei.liu2@citrix.com> > > > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > > > --- > > > tools/libxl/libxl.c | 40 ++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 40 insertions(+) > > > > > > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c > > > index 1c81239..99815a7 100644 > > > --- a/tools/libxl/libxl.c > > > +++ b/tools/libxl/libxl.c > > > @@ -4743,8 +4743,16 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > > uint32_t domid; > > > libxl__ddomain ddomain; > > > char *be_path; > > > + char **kinds = NULL, **domains = NULL, **devs = NULL; > > > + const char *sstate; > > > + char *state_path; > > > + int state; > > > + unsigned int nkinds, ndomains, ndevs; > > > + int i, j, k; > > > + xs_transaction_t t; > > > > > > ddomain.ao = ao; > > > + FILLZERO(ddomain.watch); > > > > Is this a different bugfix or stray change? > > To cleanly unregister watch and not do nothing if wasn't registered at > all. If it isn't initialized, libxl__ev_xswatch_deregister call on > not registered watch isn't harmless. Right, I've realized that before your changes the function only registered the watch and exited, this is needed now. > > > LIBXL_SLIST_INIT(&ddomain.guests); > > > > > > rc = libxl__get_domid(gc, &domid); > > > @@ -4762,9 +4770,41 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > > be_path); > > > if (rc) goto out; > > > > > > + rc = libxl__xs_transaction_start(gc, &t); > > > + if (rc) goto out; > > > > Why do you need to start a transaction here if you end up aborting it when > > finished? > > Mostly to ease error checking. Because below code does three level > listing, I don't want to deal with races where some entry was removed > between those calls, at least not here. Like this: > > xs_directory('backend/vif') -> 3, 4, 5 > xs_directory('backend/vif/3') -> 0, 1 > xs_read('backend/vif/3/0/state') -> ... > xs_read('backend/vif/3/1/state') -> ... > toolstack removes backend/vif/4 here > xs_directory('backend/vif/4') -> fail > > Of course backend_watch_callback would fail anyway in such a case, which > is ok. But having snapshot of xenstore during this multi-level listing > looks like avoiding some corner cases during listing itself. AFAICT your code seems to be prepared to deal with entries disappearing in the middle of the tree walk, so I would just remove the transaction. > > > + kinds = libxl__xs_directory(gc, t, be_path, &nkinds); > > > + if (kinds) { > > > + for (i = 0; i < nkinds; i++) { > > > + domains = libxl__xs_directory(gc, t, > > > + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); > > > + if (!domains) > > > + continue; > > > + for (j = 0; j < ndomains; j++) { > > > + devs = libxl__xs_directory(gc, t, > > > + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); > > > + if (!devs) > > > + continue; > > > + for (k = 0; k < ndevs; k++) { > > > + state_path = GCSPRINTF("%s/%s/%s/%s/state", > > > + be_path, kinds[i], domains[j], devs[k]); > > > + rc = libxl__xs_read_checked(gc, t, state_path, &sstate); > > > + if (rc) > > > + continue; > > > + state = atoi(sstate); > > > + if (state == XenbusStateInitWait) > > > + backend_watch_callback(egc, &ddomain.watch, > > > + be_path, state_path); > > > + } > > > + } > > > + } > > > + } > > > + > > > + libxl__xs_transaction_abort(gc, &t); > > > + > > > return AO_INPROGRESS; > > > > > > out: > > > + libxl__ev_xswatch_deregister(gc, &ddomain.watch); > > > > This seems to be part of a different bugfix also. > > No, this code previously wasn't reachable if xswatch was correctly > registered. Right, thanks. Roger. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 9:43 ` Roger Pau Monné @ 2016-07-11 9:49 ` Marek Marczykowski-Górecki 2016-07-11 10:00 ` Roger Pau Monné 0 siblings, 1 reply; 12+ messages in thread From: Marek Marczykowski-Górecki @ 2016-07-11 9:49 UTC (permalink / raw) To: Roger Pau Monné; +Cc: Ian Jackson, Wei Liu, xen-devel [-- Attachment #1.1: Type: text/plain, Size: 6321 bytes --] On Mon, Jul 11, 2016 at 11:43:18AM +0200, Roger Pau Monné wrote: > On Mon, Jul 11, 2016 at 10:56:04AM +0200, Marek Marczykowski-Górecki wrote: > > On Mon, Jul 11, 2016 at 10:31:17AM +0200, Roger Pau Monné wrote: > > > On Sun, Jul 10, 2016 at 07:35:47PM +0200, Marek Marczykowski-Górecki wrote: > > > > When this daemon is started after creating backend device, that device > > > > will not be configured. > > > > > > > > Racy situation: > > > > 1. driver domain is started > > > > 2. frontend domain is started (just after kicking driver domain off) > > > > 3. device in frontend domain is connected to the backend (as specified > > > > in frontend domain configuration) > > > > 4. xl devd is started in driver domain > > > > > > > > End result is that backend device in driver domain is not configured > > > > (like network interface is not enabled), so the device doesn't work. > > > > > > > > Fix this by artifically triggering events for devices already present in > > > > xenstore before xl devd is started. Do this only after xenstore watch is > > > > already registered, and only for devices not already initialized (in > > > > XenbusStateInitWait state). > > > > > > Thanks! > > > > > > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > > > > Cc: Wei Liu <wei.liu2@citrix.com> > > > > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > > > > --- > > > > tools/libxl/libxl.c | 40 ++++++++++++++++++++++++++++++++++++++++ > > > > 1 file changed, 40 insertions(+) > > > > > > > > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c > > > > index 1c81239..99815a7 100644 > > > > --- a/tools/libxl/libxl.c > > > > +++ b/tools/libxl/libxl.c > > > > @@ -4743,8 +4743,16 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > > > uint32_t domid; > > > > libxl__ddomain ddomain; > > > > char *be_path; > > > > + char **kinds = NULL, **domains = NULL, **devs = NULL; > > > > + const char *sstate; > > > > + char *state_path; > > > > + int state; > > > > + unsigned int nkinds, ndomains, ndevs; > > > > + int i, j, k; > > > > + xs_transaction_t t; > > > > > > > > ddomain.ao = ao; > > > > + FILLZERO(ddomain.watch); > > > > > > Is this a different bugfix or stray change? > > > > To cleanly unregister watch and not do nothing if wasn't registered at > > all. If it isn't initialized, libxl__ev_xswatch_deregister call on > > not registered watch isn't harmless. > > Right, I've realized that before your changes the function only registered > the watch and exited, this is needed now. > > > > > LIBXL_SLIST_INIT(&ddomain.guests); > > > > > > > > rc = libxl__get_domid(gc, &domid); > > > > @@ -4762,9 +4770,41 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > > > be_path); > > > > if (rc) goto out; > > > > > > > > + rc = libxl__xs_transaction_start(gc, &t); > > > > + if (rc) goto out; > > > > > > Why do you need to start a transaction here if you end up aborting it when > > > finished? > > > > Mostly to ease error checking. Because below code does three level > > listing, I don't want to deal with races where some entry was removed > > between those calls, at least not here. Like this: > > > > xs_directory('backend/vif') -> 3, 4, 5 > > xs_directory('backend/vif/3') -> 0, 1 > > xs_read('backend/vif/3/0/state') -> ... > > xs_read('backend/vif/3/1/state') -> ... > > toolstack removes backend/vif/4 here > > xs_directory('backend/vif/4') -> fail > > > > Of course backend_watch_callback would fail anyway in such a case, which > > is ok. But having snapshot of xenstore during this multi-level listing > > looks like avoiding some corner cases during listing itself. > > AFAICT your code seems to be prepared to deal with entries disappearing in > the middle of the tree walk, so I would just remove the transaction. Actually I'm considering changing error handling below to "goto out" instead of "continue", as race condition should be eliminated by the transaction, other errors (permission denied for example) maybe should be considered fatal. So, IMO there two options: - ignore failed reads and remove transaction - error on failed reads and keep transaction Which one would be better? > > > > + kinds = libxl__xs_directory(gc, t, be_path, &nkinds); > > > > + if (kinds) { > > > > + for (i = 0; i < nkinds; i++) { > > > > + domains = libxl__xs_directory(gc, t, > > > > + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); > > > > + if (!domains) > > > > + continue; > > > > + for (j = 0; j < ndomains; j++) { > > > > + devs = libxl__xs_directory(gc, t, > > > > + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); > > > > + if (!devs) > > > > + continue; > > > > + for (k = 0; k < ndevs; k++) { > > > > + state_path = GCSPRINTF("%s/%s/%s/%s/state", > > > > + be_path, kinds[i], domains[j], devs[k]); > > > > + rc = libxl__xs_read_checked(gc, t, state_path, &sstate); > > > > + if (rc) > > > > + continue; > > > > + state = atoi(sstate); > > > > + if (state == XenbusStateInitWait) > > > > + backend_watch_callback(egc, &ddomain.watch, > > > > + be_path, state_path); > > > > + } > > > > + } > > > > + } > > > > + } > > > > + > > > > + libxl__xs_transaction_abort(gc, &t); > > > > + > > > > return AO_INPROGRESS; > > > > > > > > out: > > > > + libxl__ev_xswatch_deregister(gc, &ddomain.watch); > > > > > > This seems to be part of a different bugfix also. > > > > No, this code previously wasn't reachable if xswatch was correctly > > registered. > > Right, thanks. > > Roger. -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 473 bytes --] [-- Attachment #2: Type: text/plain, Size: 127 bytes --] _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 9:49 ` Marek Marczykowski-Górecki @ 2016-07-11 10:00 ` Roger Pau Monné 2016-07-11 10:44 ` [PATCH v2] " Marek Marczykowski-Górecki 0 siblings, 1 reply; 12+ messages in thread From: Roger Pau Monné @ 2016-07-11 10:00 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Ian Jackson, Wei Liu, xen-devel On Mon, Jul 11, 2016 at 11:49:19AM +0200, Marek Marczykowski-Górecki wrote: > On Mon, Jul 11, 2016 at 11:43:18AM +0200, Roger Pau Monné wrote: > > On Mon, Jul 11, 2016 at 10:56:04AM +0200, Marek Marczykowski-Górecki wrote: > > > On Mon, Jul 11, 2016 at 10:31:17AM +0200, Roger Pau Monné wrote: > > > > On Sun, Jul 10, 2016 at 07:35:47PM +0200, Marek Marczykowski-Górecki wrote: > > > > > When this daemon is started after creating backend device, that device > > > > > will not be configured. > > > > > > > > > > Racy situation: > > > > > 1. driver domain is started > > > > > 2. frontend domain is started (just after kicking driver domain off) > > > > > 3. device in frontend domain is connected to the backend (as specified > > > > > in frontend domain configuration) > > > > > 4. xl devd is started in driver domain > > > > > > > > > > End result is that backend device in driver domain is not configured > > > > > (like network interface is not enabled), so the device doesn't work. > > > > > > > > > > Fix this by artifically triggering events for devices already present in > > > > > xenstore before xl devd is started. Do this only after xenstore watch is > > > > > already registered, and only for devices not already initialized (in > > > > > XenbusStateInitWait state). > > > > > > > > Thanks! > > > > > > > > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > > > > > Cc: Wei Liu <wei.liu2@citrix.com> > > > > > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > > > > > --- > > > > > tools/libxl/libxl.c | 40 ++++++++++++++++++++++++++++++++++++++++ > > > > > 1 file changed, 40 insertions(+) > > > > > > > > > > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c > > > > > index 1c81239..99815a7 100644 > > > > > --- a/tools/libxl/libxl.c > > > > > +++ b/tools/libxl/libxl.c > > > > > @@ -4743,8 +4743,16 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > > > > uint32_t domid; > > > > > libxl__ddomain ddomain; > > > > > char *be_path; > > > > > + char **kinds = NULL, **domains = NULL, **devs = NULL; > > > > > + const char *sstate; > > > > > + char *state_path; > > > > > + int state; > > > > > + unsigned int nkinds, ndomains, ndevs; > > > > > + int i, j, k; > > > > > + xs_transaction_t t; > > > > > > > > > > ddomain.ao = ao; > > > > > + FILLZERO(ddomain.watch); > > > > > > > > Is this a different bugfix or stray change? > > > > > > To cleanly unregister watch and not do nothing if wasn't registered at > > > all. If it isn't initialized, libxl__ev_xswatch_deregister call on > > > not registered watch isn't harmless. > > > > Right, I've realized that before your changes the function only registered > > the watch and exited, this is needed now. > > > > > > > LIBXL_SLIST_INIT(&ddomain.guests); > > > > > > > > > > rc = libxl__get_domid(gc, &domid); > > > > > @@ -4762,9 +4770,41 @@ int libxl_device_events_handler(libxl_ctx *ctx, > > > > > be_path); > > > > > if (rc) goto out; > > > > > > > > > > + rc = libxl__xs_transaction_start(gc, &t); > > > > > + if (rc) goto out; > > > > > > > > Why do you need to start a transaction here if you end up aborting it when > > > > finished? > > > > > > Mostly to ease error checking. Because below code does three level > > > listing, I don't want to deal with races where some entry was removed > > > between those calls, at least not here. Like this: > > > > > > xs_directory('backend/vif') -> 3, 4, 5 > > > xs_directory('backend/vif/3') -> 0, 1 > > > xs_read('backend/vif/3/0/state') -> ... > > > xs_read('backend/vif/3/1/state') -> ... > > > toolstack removes backend/vif/4 here > > > xs_directory('backend/vif/4') -> fail > > > > > > Of course backend_watch_callback would fail anyway in such a case, which > > > is ok. But having snapshot of xenstore during this multi-level listing > > > looks like avoiding some corner cases during listing itself. > > > > AFAICT your code seems to be prepared to deal with entries disappearing in > > the middle of the tree walk, so I would just remove the transaction. > > Actually I'm considering changing error handling below to "goto out" > instead of "continue", as race condition should be eliminated by the > transaction, other errors (permission denied for example) maybe should > be considered fatal. So, IMO there two options: > - ignore failed reads and remove transaction > - error on failed reads and keep transaction > > Which one would be better? IMHO, I think the first option is better, and you already have it coded. Roger. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH v2] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 10:00 ` Roger Pau Monné @ 2016-07-11 10:44 ` Marek Marczykowski-Górecki 2016-07-11 10:53 ` Roger Pau Monné 2016-07-14 9:36 ` Wei Liu 0 siblings, 2 replies; 12+ messages in thread From: Marek Marczykowski-Górecki @ 2016-07-11 10:44 UTC (permalink / raw) To: xen-devel; +Cc: Wei Liu, Ian Jackson, Marek Marczykowski-Górecki When this daemon is started after creating backend device, that device will not be configured. Racy situation: 1. driver domain is started 2. frontend domain is started (just after kicking driver domain off) 3. device in frontend domain is connected to the backend (as specified in frontend domain configuration) 4. xl devd is started in driver domain End result is that backend device in driver domain is not configured (like network interface is not enabled), so the device doesn't work. Fix this by artifically triggering events for devices already present in xenstore before xl devd is started. Do this only after xenstore watch is already registered, and only for devices not already initialized (in XenbusStateInitWait state). Cc: Ian Jackson <ian.jackson@eu.citrix.com> Cc: Wei Liu <wei.liu2@citrix.com> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> --- tools/libxl/libxl.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c index 1c81239..dd20e29 100644 --- a/tools/libxl/libxl.c +++ b/tools/libxl/libxl.c @@ -4743,6 +4743,12 @@ int libxl_device_events_handler(libxl_ctx *ctx, uint32_t domid; libxl__ddomain ddomain; char *be_path; + char **kinds = NULL, **domains = NULL, **devs = NULL; + const char *sstate; + char *state_path; + int state; + unsigned int nkinds, ndomains, ndevs; + int i, j, k; ddomain.ao = ao; LIBXL_SLIST_INIT(&ddomain.guests); @@ -4762,6 +4768,33 @@ int libxl_device_events_handler(libxl_ctx *ctx, be_path); if (rc) goto out; + kinds = libxl__xs_directory(gc, XBT_NULL, be_path, &nkinds); + if (kinds) { + for (i = 0; i < nkinds; i++) { + domains = libxl__xs_directory(gc, XBT_NULL, + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); + if (!domains) + continue; + for (j = 0; j < ndomains; j++) { + devs = libxl__xs_directory(gc, XBT_NULL, + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); + if (!devs) + continue; + for (k = 0; k < ndevs; k++) { + state_path = GCSPRINTF("%s/%s/%s/%s/state", + be_path, kinds[i], domains[j], devs[k]); + rc = libxl__xs_read_checked(gc, XBT_NULL, state_path, &sstate); + if (rc) + continue; + state = atoi(sstate); + if (state == XenbusStateInitWait) + backend_watch_callback(egc, &ddomain.watch, + be_path, state_path); + } + } + } + } + return AO_INPROGRESS; out: -- 2.5.5 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH v2] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 10:44 ` [PATCH v2] " Marek Marczykowski-Górecki @ 2016-07-11 10:53 ` Roger Pau Monné 2016-07-14 9:36 ` Wei Liu 1 sibling, 0 replies; 12+ messages in thread From: Roger Pau Monné @ 2016-07-11 10:53 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Ian Jackson, Wei Liu, xen-devel On Mon, Jul 11, 2016 at 12:44:42PM +0200, Marek Marczykowski-Górecki wrote: > When this daemon is started after creating backend device, that device > will not be configured. > > Racy situation: > 1. driver domain is started > 2. frontend domain is started (just after kicking driver domain off) > 3. device in frontend domain is connected to the backend (as specified > in frontend domain configuration) > 4. xl devd is started in driver domain > > End result is that backend device in driver domain is not configured > (like network interface is not enabled), so the device doesn't work. > > Fix this by artifically triggering events for devices already present in > xenstore before xl devd is started. Do this only after xenstore watch is > already registered, and only for devices not already initialized (in > XenbusStateInitWait state). > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > Cc: Wei Liu <wei.liu2@citrix.com> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Thanks, this looks fine to me: Acked-by: Roger Pau Monné <roger.pau@citrix.com> Roger. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH v2] libxl: trigger attach events for devices attached before xl devd startup 2016-07-11 10:44 ` [PATCH v2] " Marek Marczykowski-Górecki 2016-07-11 10:53 ` Roger Pau Monné @ 2016-07-14 9:36 ` Wei Liu 2016-07-15 23:47 ` [PATCH v3] " Marek Marczykowski-Górecki 1 sibling, 1 reply; 12+ messages in thread From: Wei Liu @ 2016-07-14 9:36 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Wei Liu, Ian Jackson, xen-devel On Mon, Jul 11, 2016 at 12:44:42PM +0200, Marek Marczykowski-Górecki wrote: > When this daemon is started after creating backend device, that device > will not be configured. > > Racy situation: > 1. driver domain is started > 2. frontend domain is started (just after kicking driver domain off) > 3. device in frontend domain is connected to the backend (as specified > in frontend domain configuration) > 4. xl devd is started in driver domain > > End result is that backend device in driver domain is not configured > (like network interface is not enabled), so the device doesn't work. > > Fix this by artifically triggering events for devices already present in > xenstore before xl devd is started. Do this only after xenstore watch is > already registered, and only for devices not already initialized (in > XenbusStateInitWait state). > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > Cc: Wei Liu <wei.liu2@citrix.com> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > --- > tools/libxl/libxl.c | 33 +++++++++++++++++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c > index 1c81239..dd20e29 100644 > --- a/tools/libxl/libxl.c > +++ b/tools/libxl/libxl.c > @@ -4743,6 +4743,12 @@ int libxl_device_events_handler(libxl_ctx *ctx, > uint32_t domid; > libxl__ddomain ddomain; > char *be_path; > + char **kinds = NULL, **domains = NULL, **devs = NULL; > + const char *sstate; > + char *state_path; > + int state; > + unsigned int nkinds, ndomains, ndevs; > + int i, j, k; > > ddomain.ao = ao; > LIBXL_SLIST_INIT(&ddomain.guests); > @@ -4762,6 +4768,33 @@ int libxl_device_events_handler(libxl_ctx *ctx, > be_path); > if (rc) goto out; > > + kinds = libxl__xs_directory(gc, XBT_NULL, be_path, &nkinds); > + if (kinds) { > + for (i = 0; i < nkinds; i++) { > + domains = libxl__xs_directory(gc, XBT_NULL, > + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); > + if (!domains) > + continue; > + for (j = 0; j < ndomains; j++) { > + devs = libxl__xs_directory(gc, XBT_NULL, > + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); > + if (!devs) > + continue; > + for (k = 0; k < ndevs; k++) { > + state_path = GCSPRINTF("%s/%s/%s/%s/state", > + be_path, kinds[i], domains[j], devs[k]); > + rc = libxl__xs_read_checked(gc, XBT_NULL, state_path, &sstate); > + if (rc) > + continue; > + state = atoi(sstate); Need to check sstate != NULL before passing it to atoi, because libxl__xs_read_checked can return NULL if there is no such entry in xenstore. > + if (state == XenbusStateInitWait) > + backend_watch_callback(egc, &ddomain.watch, > + be_path, state_path); Nit, indentation. Wei. > + } > + } > + } > + } > + > return AO_INPROGRESS; > > out: > -- > 2.5.5 > _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH v3] libxl: trigger attach events for devices attached before xl devd startup 2016-07-14 9:36 ` Wei Liu @ 2016-07-15 23:47 ` Marek Marczykowski-Górecki 2016-07-18 15:31 ` Wei Liu 0 siblings, 1 reply; 12+ messages in thread From: Marek Marczykowski-Górecki @ 2016-07-15 23:47 UTC (permalink / raw) To: xen-devel; +Cc: Wei Liu, Ian Jackson, Marek Marczykowski-Górecki When this daemon is started after creating backend device, that device will not be configured. Racy situation: 1. driver domain is started 2. frontend domain is started (just after kicking driver domain off) 3. device in frontend domain is connected to the backend (as specified in frontend domain configuration) 4. xl devd is started in driver domain End result is that backend device in driver domain is not configured (like network interface is not enabled), so the device doesn't work. Fix this by artifically triggering events for devices already present in xenstore before xl devd is started. Do this only after xenstore watch is already registered, and only for devices not already initialized (in XenbusStateInitWait state). Cc: Ian Jackson <ian.jackson@eu.citrix.com> Cc: Wei Liu <wei.liu2@citrix.com> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> --- Changes since v2: - check for sstate being NULL - minor indentation tools/libxl/libxl.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c index 1c81239..b69466f 100644 --- a/tools/libxl/libxl.c +++ b/tools/libxl/libxl.c @@ -4743,6 +4743,12 @@ int libxl_device_events_handler(libxl_ctx *ctx, uint32_t domid; libxl__ddomain ddomain; char *be_path; + char **kinds = NULL, **domains = NULL, **devs = NULL; + const char *sstate; + char *state_path; + int state; + unsigned int nkinds, ndomains, ndevs; + int i, j, k; ddomain.ao = ao; LIBXL_SLIST_INIT(&ddomain.guests); @@ -4762,6 +4768,33 @@ int libxl_device_events_handler(libxl_ctx *ctx, be_path); if (rc) goto out; + kinds = libxl__xs_directory(gc, XBT_NULL, be_path, &nkinds); + if (kinds) { + for (i = 0; i < nkinds; i++) { + domains = libxl__xs_directory(gc, XBT_NULL, + GCSPRINTF("%s/%s", be_path, kinds[i]), &ndomains); + if (!domains) + continue; + for (j = 0; j < ndomains; j++) { + devs = libxl__xs_directory(gc, XBT_NULL, + GCSPRINTF("%s/%s/%s", be_path, kinds[i], domains[j]), &ndevs); + if (!devs) + continue; + for (k = 0; k < ndevs; k++) { + state_path = GCSPRINTF("%s/%s/%s/%s/state", + be_path, kinds[i], domains[j], devs[k]); + rc = libxl__xs_read_checked(gc, XBT_NULL, state_path, &sstate); + if (rc || !sstate) + continue; + state = atoi(sstate); + if (state == XenbusStateInitWait) + backend_watch_callback(egc, &ddomain.watch, + be_path, state_path); + } + } + } + } + return AO_INPROGRESS; out: -- 2.5.5 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH v3] libxl: trigger attach events for devices attached before xl devd startup 2016-07-15 23:47 ` [PATCH v3] " Marek Marczykowski-Górecki @ 2016-07-18 15:31 ` Wei Liu 2016-07-19 13:20 ` Wei Liu 0 siblings, 1 reply; 12+ messages in thread From: Wei Liu @ 2016-07-18 15:31 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Wei Liu, Ian Jackson, xen-devel On Sat, Jul 16, 2016 at 01:47:56AM +0200, Marek Marczykowski-Górecki wrote: > When this daemon is started after creating backend device, that device > will not be configured. > > Racy situation: > 1. driver domain is started > 2. frontend domain is started (just after kicking driver domain off) > 3. device in frontend domain is connected to the backend (as specified > in frontend domain configuration) > 4. xl devd is started in driver domain > > End result is that backend device in driver domain is not configured > (like network interface is not enabled), so the device doesn't work. > > Fix this by artifically triggering events for devices already present in > xenstore before xl devd is started. Do this only after xenstore watch is > already registered, and only for devices not already initialized (in > XenbusStateInitWait state). > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > Cc: Wei Liu <wei.liu2@citrix.com> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Acked-by: Wei Liu <wei.liu2@citrix.com> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH v3] libxl: trigger attach events for devices attached before xl devd startup 2016-07-18 15:31 ` Wei Liu @ 2016-07-19 13:20 ` Wei Liu 0 siblings, 0 replies; 12+ messages in thread From: Wei Liu @ 2016-07-19 13:20 UTC (permalink / raw) To: Marek Marczykowski-Górecki; +Cc: Wei Liu, Ian Jackson, xen-devel On Mon, Jul 18, 2016 at 04:31:30PM +0100, Wei Liu wrote: > On Sat, Jul 16, 2016 at 01:47:56AM +0200, Marek Marczykowski-Górecki wrote: > > When this daemon is started after creating backend device, that device > > will not be configured. > > > > Racy situation: > > 1. driver domain is started > > 2. frontend domain is started (just after kicking driver domain off) > > 3. device in frontend domain is connected to the backend (as specified > > in frontend domain configuration) > > 4. xl devd is started in driver domain > > > > End result is that backend device in driver domain is not configured > > (like network interface is not enabled), so the device doesn't work. > > > > Fix this by artifically triggering events for devices already present in > > xenstore before xl devd is started. Do this only after xenstore watch is > > already registered, and only for devices not already initialized (in > > XenbusStateInitWait state). > > > > Cc: Ian Jackson <ian.jackson@eu.citrix.com> > > Cc: Wei Liu <wei.liu2@citrix.com> > > Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> > > Acked-by: Wei Liu <wei.liu2@citrix.com> Queued. Thanks. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel ^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2016-07-19 13:20 UTC | newest] Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2016-07-10 17:35 [PATCH] libxl: trigger attach events for devices attached before xl devd startup Marek Marczykowski-Górecki 2016-07-11 8:31 ` Roger Pau Monné 2016-07-11 8:56 ` Marek Marczykowski-Górecki 2016-07-11 9:43 ` Roger Pau Monné 2016-07-11 9:49 ` Marek Marczykowski-Górecki 2016-07-11 10:00 ` Roger Pau Monné 2016-07-11 10:44 ` [PATCH v2] " Marek Marczykowski-Górecki 2016-07-11 10:53 ` Roger Pau Monné 2016-07-14 9:36 ` Wei Liu 2016-07-15 23:47 ` [PATCH v3] " Marek Marczykowski-Górecki 2016-07-18 15:31 ` Wei Liu 2016-07-19 13:20 ` Wei Liu
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