This makes freezing a namespace an irrevocable operation but in return allows
omitting further lock operations. This results in a performance improvement as
reading an atomic bool is faster than acquiring and releasing a shared lock.
ObjectLocks on namespaces remain untouched as these mostly affect write
operations which there should be none of after freezing (if there are some,
they will throw exceptions anyways).
This commit removes EmbeddedNamespaceValue and ConstEmbeddedNamespaceValue and
reduces NamespaceValue down to a simple struct without inheritance or member
functions. The code from these clases is inlined into the Namespace class. The
class hierarchy determining whether a value is const is moved to an attribute
of NamespaceValue.
This is done in preparation for changes to the locking in the Namespace class.
Currently, it relies on a recursive mutex. In the future, a shared mutex
(read/write lock) should be used instead, which cannot allow recursive locking
(without failing or risk deadlocking on lock upgrades). With this change, all
operations requiring a lock for one operation are within one function, no
recursive locking is not needed any more.
This commit adds a new initialization priority `FreezeNamespaces` that is run
last and moves all calls to `Namespace::Freeze()` there. This allows all other
initialization functions to still update namespaces without the use of the
`overrideFrozen` flag.
It also moves the initialization of `System.Platform*` and `System.Build*` to
an initialize function so that these can also be set without setting
`overrideFrozen`.
This is preparation for a following commit that will make the frozen flag in
namespaces finial, no longer allowing it to be overriden (freezing the
namespace will disable locking, so performing further updates would be unsafe).
Change the type of the priority values from int to a new enum. By replacing the
magic int values throughout the code base with named values, there is now a
single place where all priority values are defined and you get an overview over
the initialization order.
In essence, namespace behaviors acted as hooks for update operations on
namespaces. Two behaviors were implemented:
- `NamespaceBehavior`: allows the update operation unless it acts on a value
that itself was explicitly marked as constant.
- `ConstNamespaceBehavior`: initially allows insert operations but marks the
individual values as const. Additionally provides a `Freeze()` member
function. After this was called, updates are rejected unless a special
`overrideFrozen` flag is set explicitly.
This marvel of object-oriented programming can be replaced with a simple bool.
This commit basically replaces `Namespace::m_Behavior` with
`Namespace::m_ConstValues` and inlines the behavior functions where they were
called. While doing so, the code was slightly simplified by assuming that
`m_ConstValues` is true if `m_Frozen` is true. This is similar to what the API
allowed in the old code as you could only freeze a `ConstNamespaceBehavior`.
However, this PR moves the `Freeze()` member function and the related
`m_Freeze` member variable to the `Namespace` class. So now the API allows any
namespace to be frozen. The new code also makes sense with the previously
mentioned simplification: a `Namespace` with `m_ConstValues = false` can be
modified without restrictions until `Freeze()` is called. When this is done, it
becomes read-only.
The changes outside of `namespace.*` just adapt the code to the slightly
changed API.
1. The lookup of apply rules per source type now implies
no String(const char*) (no malloc()) and just pointer (uint64) comparisions
2. Apply rules are now also grouped by target type via a nested map, that obsoletes
checking the target type while iterating over all rules per source type
Apparently there was a reason for making the members of generated classes
atomic. However, this was only done for some types, others were still accessed
using non-atomic operations. For members of type T::Ptr (i.e. intrusive_ptr<T>),
this can result in a double free when multiple threads access the same variable
and at least one of them writes to the variable.
This commit makes use of std::atomic<T> for more T (it removes the additional
constraint sizeof(T) <= sizeof(void*)) and uses a type including a mutex for
load and store operations as a fallback.
Checkable::FireSuppressedNotifications() compares the time of the current
checkable with the last recovery time of parents to avoid notification right
after a parent recovered and before the current checkable was checked.
This commit makes this check also include to host if the checkable is a
service. This makes the behavior consistent with the documentation that states
there is an implicit dependency on the host (which isn't realized as implicitly
generating a Dependency object unfortunately).
This commit changes the Checkable notification suppression logic (notifications
are currently suppressed on the Checkable if it is unreachable, in a downtime,
or acknowledged) to that after the suppression reason ends, a state
notification is sent if and only if the first hard state after is different
from the last hard state from before. If the checkable is in a soft state after
the suppression ends, the notification is further suppressed until a hard state
is reached.
To achieve this behavior, a new attribute state_before_suppression is added to
Checkable. This attribute is set to the last hard state the first time either a
PROBLEM or a RECOVERY notification is suppressed. Compared to from before,
neither of these two flags in the suppressed_notification will ever be cleared
while the supression is still ongoing but only after the suppression ended and
the current state is compared with the old state stored in
state_before_suppression.
Without this commit, children and parents of a checkable were rescheduled on a
state change while holding the lock for the current checkable. If both ends of
a dependency are checked at the same time and both change state, they could end
up in a deadlock waiting for each other.
This commit fixes this problem by changing the code so that other checkables
are rescheduled only after releasing the lock for the current checkable.
to ensure Checkable#IsReachable() returns correctly for dependency children inside OnReachabilityChanged().
That needs the dependency parent to be already in the correct state.
refs #9143
Alexander A. Klimov
Julian Brost
Yonas Habteab
Damiano Chini