| Commit message (Collapse) | Author | Age | Files | Lines |
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This is less fragile, and more in keeping with the usual style of
initialising everything to 0 and freeing things unconditionally.
Correspondingly, remove the tests at the call sites.
Apropos of c1f3f174. No overall functional change.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
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Coverity-ID: 1055292
Signed-off-by: Matthew Daley <mattjd@gmail.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
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Because there is not necessarily any lock held at the point the
application (eg, libvirt) calls libxl_osevent_occurred_timeout, in a
multithreaded program those calls may be arbitrarily delayed in
relation to other activities within the program.
Specifically this means when ->timeout_deregister returns, libxl does
not know whether it can safely dispose of the for_libxl value or
whether it needs to retain it in case of an in-progress call to
_occurred_timeout.
The interface could be fixed by requiring the application to make a
new call into libxl to say that the deregistration was complete.
However that new call would have to be threaded through the
application's event loop; this is complicated and some application
authors are likely not to implement it properly. Furthermore the
easiest way to implement this facility in most event loops is to queue
up a time event for "now".
Shortcut all of this by having libxl always call timeout_modify
setting abs={0,0} (ie, ASAP) instead of timeout_deregister. This will
cause the application to call _occurred_timeout. When processing this
calldown we see that we were no longer actually interested and simply
throw it away.
Additionally, there is a race between _occurred_timeout and
->timeout_modify. If libxl ever adjusts the deadline for a timeout
the application may already be in the process of calling _occurred, in
which case the situation with for_app's lifetime becomes very
complicated. Therefore abolish libxl__ev_time_modify_{abs,rel} (which
have no callers) and promise to the application only ever to call
->timeout_modify with abs=={0,0}. The application still needs to cope
with ->timeout_modify racing with its internal function which calls
_occurred_timeout. Document this.
This is a forwards-compatible change for applications using the libxl
API, and will hopefully eliminate these races in callback-supplying
applications (such as libvirt) without the need for corresponding
changes to the application. (It is possible that this might expose
bugs in applications, though, as previously libxl would never call
libxl_osevent_hooks->timeout_modify and now it never calls
->timeout_deregister).
For clarity, fold the body of time_register_finite into its one
remaining call site. This makes the semantics of ev->infinite
slightly clearer.
Cc: Bamvor Jian Zhang <bjzhang@suse.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Tested-by: Jim Fehlig <jfehlig@suse.com>
Acked-by: Jim Fehlig <jfehlig@suse.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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Because there is not necessarily any lock held at the point the
application (eg, libvirt) calls libxl_osevent_occurred_timeout and
..._fd, in a multithreaded program those calls may be arbitrarily
delayed in relation to other activities within the program.
libxl therefore needs to be prepared to receive very old event
callbacks. Arrange for this to be the case for fd callbacks.
This requires a new layer of indirection through a "hook nexus" struct
which can outlive the libxl__ev_foo. Allocation and deallocation of
these nexi is mostly handled in the OSEVENT macros which wrap up
the application's callbacks.
Document the problem and the solution in a comment in libxl_event.c
just before the definition of struct libxl__osevent_hook_nexus.
There is still a race relating to libxl__osevent_occurred_timeout;
this will be addressed in the following patch.
Reported-by: Bamvor Jian Zhang <bjzhang@suse.com>
Cc: Bamvor Jian Zhang <bjzhang@suse.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Tested-by: Jim Fehlig <jfehlig@suse.com>
Acked-by: Jim Fehlig <jfehlig@suse.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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When deregistering a timeout, the address of application data was
being passed to the timeout_deregister hook instead of the data
itself.
Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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This avoids us having to think about the error handling on failure.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
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This was ommited in the majority of cases. Add as a parameter to
libxl__event_new and the NEW_EVENT wrapper to help prevent it being
forgotten in the future.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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It was convenient to invent $(CFLAGS_LIBXL) to do this.
Various renamings to avoid shadowing standard functions:
- index(3)
- listen(2)
- link(2)
- abort(3)
- abs(3)
Reduced the scope of some variables to avoid conflicts.
Change to libxc is due to the nested hypercall buf macros in
set_xen_guest_handle (used in libxl) using the same local private vars.
Build tested only.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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Previously we only initialised it if an explicit keyvar_init_val was
given but not if the default was implicitly 0.
In the generated code this only changes the unused libxl_event_init_type
function:
void libxl_event_init_type(libxl_event *p, libxl_event_type type)
{
+ assert(!p->type);
+ p->type = type;
switch (p->type) {
case LIBXL_EVENT_TYPE_DOMAIN_SHUTDOWN:
break;
However I think it is wrong that this function is unused, this and
libxl_event_init should be used by libxl__event_new. As it happens
both are just memset to zero but for correctness we should use the
init functions (in case the IDL changes).
In the generator we also need to properly handle init_var == 0 which
the current if statements incorrectly treat as False. This doesn't
actually have any impact on the generated code.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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In afterpoll_internal, the callback functions may register and
deregister events arbitrarily. This means that we need to consider
the reentrancy-safety of the event machinery state variables.
Most of the code is safe but the fd handling is not. Fix this by
arranging to restart the fd scan loop every time we call one of these
callback functions.
For this loop to terminate, we modify afterpoll_check_fd so that it
returns only once for each of afterpoll's efds.
Another possible solution would be simply to return from
afterpoll_internal after calling efd->func. That would be a small and
more obviously correct change but would prevent the process from
handling more than one fd event with a single call to poll.
This is apropos of a report from Roger Pau Monne to me (pers.comm.)
of this crash on NetBSD:
Program terminated with signal 11, Segmentation fault.
#0 0x00007f7ff743131b in afterpoll_check_fd (poller=<optimized out>, fds=0x7f7ff7b241c0, nfds=7, fd=-1, events=1)
at libxl_event.c:856
856 if (fds[slot].fd != fd)
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Reported-by: Roger Pau Monne <roger.pau@citrix.com>
Tested-by: Roger Pau Monne <roger.pau@citrix.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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On entry to libxl__ao_progress_report, the caller has allocated an
event. If the progress report is to be ignored, we need to free it.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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In 25182:6c3345d7e9d9 the practice of passing NULL to gc-using memory
allocation functions was introduced. However, the arrangements there
were not correct as committed, because the error handling and logging
depends on getting a ctx from the gc - so an allocation error would in
fact result in libxl dereferencing NULL.
Instead, provide a special dummy gc in the ctx, called `nogc_gc'. It
is marked out specially by having alloc_maxsize==-1, which is
otherwise invalid.
Functions which need to actually look into the gc use the new test
function gc_is_real (whose purpose is mainly clarity of the code) to
check whether the gc is the dummy one, and do nothing if it is. And
we provide a helper macro NOGC which uses the in-scope real gc to find
the ctx and hence the dummy gc (and which replaces the previous
#define NOGC NULL).
Change all callers which pass 0 or NULL to an allocation function to
use NOGC or &ctx->nogc_gc, as applicable in the context.
We add a comment near the definition of LIBXL_INIT_GC pointing out
that it isn't any more the only place a libxl__gc struct is
initialised, for the benefit of anyone changing the contents of gc's
in the future.
Also, actually document that libxl__ptr_add is legal with ptr==NULL,
and change a couple of calls not to check for NULL argument.
Reported-by: Bamvor Jian Zhang <bjzhang@suse.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Bamvor Jian Zhang <bjzhang@suse.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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(In libxl__ao_complete_check_progress_reports, introduce libxl_ctx *ctx.)
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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* Add debugging output for register/deregister.
* Make the debugging printfs consistent about the order in which they
print the information.
* Where we touch the code, change LIBXL__LOG to LOG.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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We need to call libxl__free_all after egc_run_callbacks since some of
the callbacks might be ao progress reports allocated from the egc's
gc.
Fixes a segfault in egc_run_callbacks.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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This will catch earlier the mistake where an ao is completed while it
still has events registered: when the event callback happens for the
long-gone ao, we will crash before attempting to execute any of the
operation-specific code.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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Cancel the bootloader (specifically, by sending it a signal) if the
domain is seen to disappear from xenstore.
We use a new utility event source libxl__domaindeathcheck which
provides a convenient wrapper for the xenstore watch.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Changes since v8:
* Fixed the commit message summary line.
Changes since v7:
* Add a comment explaining why we use a watch on the domain's
xenstore path rather than @releaseDomain.
* Fix typo in error message.
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Change to use libxl__zalloc, where allocation failure is fatal.
Also remove a spurious semicolon from the helper macro.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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This will be used for reporting, during domain creation, that the
console is ready.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Changes since v7:
* If aop->how.callback, actually add the aop to the for_callback list (!)
* Document the threadsafety of aop's, and make appropriate cross-references.
* Allocate the actual aop from its thread's egc; do not free it.
* Remove pointless code motion of libxl__ao_create.
* Minor formatting fixes.
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Document the concurrent access policies for libxl__ao and libxl__egc,
and their corresponding gcs.
Fix a violation of the policy:
If an ao was submitted and a callback requested, and while the
initiating function was still running on the original thread, the ao
is completed on another thread, the completing thread would improperly
concurrently access the ao with the initiating thread.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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SIGCHLD or not; if it does, it has to tell us about deaths of our
children.
Currently there are no callers in libxl which use these facilities.
All code in libxl which forks needs to be converted and libxl_fork
needse to be be abolished.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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We need a slightly more sophisticated data structure to allow this,
where we record the slot not just for each fd but also for each
(fd,eventbit) where eventbit is POLLIN, POLLPRI, POLLOUT.
Document the new relaxed restriction.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Changes since v6:
* Fix typo
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Pass POLLERR and POLLHUP to fd callbacks, as is necessary.
Crash on POLLNVAL since that means our fds are messed up.
Document the behaviour (including the fact that poll sometimes sets
POLLHUP or POLLERR even if only POLLIN was requested.
Fix the one current fd callback to do something with POLLERR|POLLHUP.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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The OSEVENT_HOOK_INTERN macro incorrectly returned the value of the
expression CTX->osevent_in_hook-- (usually 1) instead of the value of
the function call it made. Fix the macro to return the proper value.
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
tools/libxl/libxl_event.c | 28 ++++++++++++++++------------
1 files changed, 16 insertions(+), 12 deletions(-)
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Introduce definition and use of a new function-local macro REQUIRE_FDS
to avoid repeatedly spelling out which fds we are interested in.
We are going to introduce a new fd for the SIGCHLD self-pipe.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Remove poller from the list once it has been requested.
Fixes a double-free bug.
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Acked-by: Ian Jackson <ian.jackson@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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eventloop_iteration's head comment says that it must be called with
the ctx locked exactly once, and this is indeed true, and it's done
correctly at both the call sites.
However, it takes out the lock an additional time itself. This is
wrong because it prevents the unlocks around poll from being
effective. This would mean that a multithreaded event-loop using
program might suffer from undesired blocking, as one thread trying to
enter libxl might end up stalled by another thread waiting for a slow
event. So remove those two lock calls.
Also add a couple of comments documenting the locking behaviour of
libxl__ao_inprogress and libxl__egc_cleanup.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Make it possible to complete an ao during its initating function.
Previously this was not generally possible because initiators did not
have an egc. But there is no reason why an ao initiator should not
have an egc, so make the standard macros provide one.
Change the internal documentation comments accordingly. (This change,
which means that an initiator function may call a completion callback
directly, is already consistent with the documented external API.)
We also invent of a new state flag "constructing" which indicates
whether we are between ao__create and ao__inprogress. This is a
slightly optimisation which allows ao_complete to not bother poking
the wakeup pipe, since the logic in ao__inprogress will not run the
event loop if the ao is complete on entry.
Also fix the wording in the libxl_internal.h comment forbidding use of
ao_how-taking functions from within libxl. (There are sadly currently
some such functions.)
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Roger Pau Monne <roger.pau@entel.upc.edu>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Provide a new-style asynchronous facility for waiting for device
states on xenbus. This will replace libxl__wait_for_device_state,
after the callers have been updated in later patches.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Provide a new set of machinery for writing public libxl functions
which may take a long time. The application gets to decide whether
they want the function to be synchronous, or whether they'd prefer to
get a callback, or an event, when the operation is complete.
User(s) of this machinery will be introduced in later patch(es).
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Previously, the context would be locked whenever we were waiting in
libxl's own call to poll (waiting for operating system events).
This would mean that multiple simultaneous calls to libxl_event_wait
in different threads with different parameters would not work
properly.
If we simply unlock the context, it would be possible for another
thread to discover the occurrence of the event we were waiting for,
without us even waking up, and we would remain in poll. So we need a
way to wake up other threads: a pipe, one for each thread in poll.
We also need to move some variables from globals in the ctx to be
per-polling-thread.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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Replace the existing API for retrieving high-level events (events
about domains, etc.) from libxl with a new one.
This changes the definition and semantics of the `libxl_event'
structure, and replaces the calls for obtaining information about
domain death and disk eject events.
This is an incompatible change, sorry. The alternative was to try to
provide both the previous horrid API and the new one, and would also
involve never using the name `libxl_event' for the new interface.
The new "libxl_event" structure is blacklisted in the ocaml bindings
for two reasons:
- It has a field name "type" (which is a keyword in ocaml);
the ocaml idl generator should massage this field name on
output, to "type_" perhaps.
- The ocaml idl generator does not support KeyedUnion.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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We provide a new set of functions and related structures
libxl_osevent_*
which are to be used by event-driven applications to receive
information from libxl about which fds libxl is interested in, and
what timeouts libxl is waiting for, and to pass back to libxl
information about which fds are readable/writeable etc., and which
timeouts have occurred. Ie, low-level events.
In this patch, this new machinery is still all unused. Callers will
appear in the next patch in the series, which introduces a new API for
applications to receive high-level events about actual domains etc.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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