This pref does not override privacy.resistFingerprinting, but when it is set (and
privacy.resistFingerprinting is not) we will still adjust the precision of almost
all timers. The adjustment amount is the second pref, which is defaulted to
20us but now dynamically adjustable (in the scale of microseconds.)
This patch does _not_ address the performance API, which privacy.resistFingerprinting
disables.
We are landing this preffed on at the current value we clamp performance.now() at
which is 20us.
MozReview-Commit-ID: ESZlSvH9w1D
This patch introduces three keyed histograms:
- PREFERENCES_FILE_LOAD_SIZE_B
- PREFERENCES_FILE_LOAD_NUM_PREFS
- PREFERENCES_FILE_LOAD_TIME_US
They are all keyed on the prefs file's name; in my local Linux64 build there
are 13 such files.
Because prefs start up earlier than telemetry, we have to save the measurements
and then pass them to telemetry later.
MozReview-Commit-ID: H6KD7oeK8O0
Currently pref_ReadPrefFromJar() will return NS_OK if parsing fails. This is
weird, and inconsistent with openPrefFile().
MozReview-Commit-ID: 7cHSewQYymE
New content processes get prefs in three ways.
- They read them from greprefs.js, prefs.js and other such files.
- They get sent "early prefs" from the parent process via the command line
(-intPrefs/-boolPrefs/-stringPrefs).
- They get sent "late prefs" from the parent process via IPC message.
(The latter two are necessary for communicating prefs that have been added or
modified in the parent process since the file reading occurred at startup.)
We have some machinery that detects if a late pref is accessed before the late
prefs are set, which is good. But it has a big exception in it; late pref
accesses that occur early via Add*VarCache() and RegisterCallbackAndCall() are
allowed.
This exception was added in bug 1341414. The description of that bug says "We
should change AddBoolVarCache so that it doesn't look at the pref in the
content process until prefs have been received from the parent." Unfortunately,
the patch in that bug added the exception to the checking without changing
Add*VarCache() in the suggested way!
This means it's possible for late prefs to be read early via VarCaches (or
RegisterCallbackAndCall()) when their values are incorrect, which is bad.
Changing Add*VarCache() to delay the reading as bug 1341414 originally
suggested seems difficult. A simpler fix is to just remove the exception in the
checking and extend the early prefs list as necessary. This patch does that,
lengthening the early prefs list from ~210 to ~300. Fortunately, most (all?) of
the added prefs are ints or bools rather than strings, so it doesn't increase
the size of the command line arguments for content processes by too much.
This code is used to detect too-early accesses of prefs in content processes.
The patch makes the following changes.
- New terminology: "early" prefs are those sent via the command line; "late"
prefs are those sent via IPC. Previously the former were "init" prefs and the
latter didn't have a clear name.
- The phase tracking and checking is now almost completely encapsulated within
Preferences.cpp. The only exposure to outside code is via the
AreAllPrefsSetInContentProcess() method, which has a single use.
- The number of states tracked drops from 5 to 3. There's no need to track the
beginning of the pref-setting operations, because we only need to know if
they've finished. (This also avoids the weirdness where we could transition
from END_INIT_PREFS back to BEGIN_INIT_PREFS because of the way -intPrefs,
-boolPrefs and -stringPrefs were parsed separately.)
MozReview-Commit-ID: IVJWiDxdsDV
The default path and the user path are entirely disjoint, and some of the
arguments only apply to one of the paths, so splitting it into two functions
makes things a bit clearer. The aForceSet arg is also renamed aFromFile.
MozReview-Commit-ID: LYtrwz5JHiN
pref_SetPref() is now the only function that runs in the content process and
calls HandleDirty(). So this patch moves the parent process check out of
HandleDirty() into pref_SetPref().
The patch also adds assertions to a couple of other parent-process-only
functions.
MozReview-Commit-ID: KurXKMl4IIb
The code to migrate from the toolkit.telemetry.enabledPreRelease pref to
toolkit.telemetry.enabled was added to Firefox 31 in bug 986582. It should be
safe to remove now.
MozReview-Commit-ID: JBkn20bUQXx
Preferences::SetPreference() is used when setting prefs in the content process
from dom::Pref values that are passed from the parent process. Currently we
use the high-level Set*InAnyProcess() methods to do this -- basically the same
code path as sets done via the API -- but this has several problems.
- It is subtly broken. If the content process already has a pref of type T with
a default value and then we get a SetPreference() call that tries to change
it to type U, it will erroneously fail. In practice this never(?) happens,
but it shows that things aren't arranged very well.
- SetPreference() also looks up the hashtable twice to get the same pref if
both a default value and a user value are present in the dom::Pref.
- This happens in content processes, while all other pref set operations occur
in the parent process. This is the main reason we have the Set*InAnyProcess()
functions.
In short, the setting of prefs via IPC is quite different to the setting of
prefs via other means -- because it happens in content processes, and it's more
of a clobber that can set both values at once -- and so should be handled
differently.
The solution is to make Preferences::SetPreference() use lower-level operations
to do the update. It now does the hash table lookup/add itself, and then calls
the new Pref::FromDomPref() method. That method then possibly calls the new
PrefValue::FromDomPrefValue() method for both kinds of value, and overwrites
them as necessary. SetValueFromDom() is no longer used and the patch removes it.
MozReview-Commit-ID: 2Rg8VMOc0Cl
The nice thing about this is that the memory management of the strings
(moz_xstrdup() and free()) is now entirely within PrefValue.
MozReview-Commit-ID: KJjnURpmgfE
It's something of an obfuscation, and it forces together various bool values
that don't necessarily have to be together (and won't be together after future
refactorings).
The patch also reorders some function arguments for consistency: PrefType, then
PrefValueKind, then PrefValue.
MozReview-Commit-ID: KNY0Pxo0Nxf
Although it is a subclass of PLDHashEntryHdr, it's the main representation of a
pref, so the name should reflect that.
MozReview-Commit-ID: 5qJNQtjbFmH
As is done in pref_SavePrefs().
The confusion here is because a Vector can fill 100% of its capacity, but a
hash table cannot go past 75% of its capacity.
MozReview-Commit-ID: 5JMbmtrxMGN
It represents a pref, so `Pref` is a better name. Within Preferences.cpp the
patch uses domPref/aDomPref to distinguish it from PrefHashEntry values.
MozReview-Commit-ID: HXTl0GX4BtO
This factors out some common code from SetValue(), making it easier to read.
The patch also improves the comments in SetValue().
MozReview-Commit-ID: 60JnBlIS1q6
Currently, you can create a pref that only has a user value, and then later
give it a default value with a different type. The entire pref is then recorded
as having this second type. This causes problems later when interpreting the
user value.
This patch makes SetValue() fail if it tries to set a default value whose type
differs from an existing user value. It also expands an existing test to cover
this case and some similar ones.
MozReview-Commit-ID: 89tvISQ7RNT
This requires adding an aPriority argument (defaulting to false) to
Preferences::RegisterCallback(). And RegisterVarCacheCallback() is no longer
necessary.
MozReview-Commit-ID: BMDk3HuaQVV
We can move the setting into ReplaceValue() and ClearValue(), and then those
methods aren't needed any more.
The patch also removes some getter calls within PrefHashEntry by directly using
field names.
MozReview-Commit-ID: 42EAx1Kh9Et
There's an "XXX" comment suggesting a possible leak when string user values are
cleared. Turns out a lot of the time there won't be a leak, because the string
pointer isn't overwritten and ClearEntry() frees the string when the pref is
destroyed. However, if the user value is subsequently overwritten with a
different string, there will be a leak. Also, even in the non-leak case, we
currently hold onto the string for longer than necessary.
This patch introduces ClearUserValue() -- which frees the string when
appropriate -- and uses it in all the places where values are cleared.
MozReview-Commit-ID: ARuWUNzPTfy
Specifically:
- rename it as NotifyCallbacks();
- remove the return value, because it is always NS_OK;
- some minor naming and declaration clean-ups.
MozReview-Commit-ID: GcH81owPLsp
