Create a second set of system properties, that can be overlaid over the
real ones if necessary, for appcompat purposes.
Bug: 291814949
Ignore-AOSP-First: Aosp -> internal merge conflict
Test: manual, treehugger, system_properties_test
Change-Id: I541d3658cab7753c16970957c6ab4fc8bd68d8f3
Merged-In: I884a78b67679c1f0b90a6c0159b17ab007f8cc60
Change our handful of `constexpr static`s to the much more common
`static constexpr`. It's easier to "follow existing style" when there
aren't two existing styles to copy from, and all else being equal,
"majority wins" :-)
Test: treehugger
Change-Id: Ifbf0f62ab84c9450bf9c2e49e96915c126fd20c4
These should never be particularly long, but because this code runs
before we can allocate, they have to be fixed size. Bring that size down
to 128 bytes which should be enough for anyone, and which should let us
add some new filenames in less space than we're currently using for one
filename.
Test: treehugger
Change-Id: I524d7e5ffd415ba0c3d600eb94801a304b1b4bb4
Presumably "bt" was "binary tree", but "trie_node" is a bit more
specific and removes the guesswork.
Test: treehugger
Change-Id: Ib5fb2dcbcf261ce516728099d484ed9cd6c069bd
Revert submission 1403568-sysprop_trace
Reason for revert: makes property get/set non-reentrant
Reverted Changes:
I6f85f3f52:Add systrace tag for system property
Id2b93acb2:Adding system property tracing
Id78992d23:Add systrace tag for system property
I1ba9fc7bd:Add systrace tag for system property
Bug: 193050299
Test: build and boot a device
Change-Id: Ic7a83fb01a39113d408ed0c95d27f694d5a2649c
This benchmarks mapping property prefixes to property contexts with
two algorithms: the 'Legacy' method used before Android P and the
'Trie' used afterwards (the code in this directory).
It uses input mappings from both Oreo and the latest in AOSP ('S').
Note that there is nearly a 10x increase in the number of mappings in
S as there was in Oreo, which was predicted when the trie was
designed.
Results on cuttlefish:
-----------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------
LegacyLookupOreo 683576 ns 673538 ns 1060
LegacyLookupS 5683109 ns 5596982 ns 124
TrieLookupOreo 299851 ns 295696 ns 2378
TrieLookupS 584831 ns 576801 ns 1204
The results show that the legacy look up uses 8.3x more CPU time to
handle the number of mappings added through S, whereas the Trie lookup
uses less than 2x more CPU time, showing that the trie scales better
with added mappings.
Test: run this benchmark
Change-Id: I35c3aa4429f049e327a891f9cbe1901d8855d7ba
Introducing a new systrace tag, TRACE_TAG_SYSPROP, for use with
system property.
For property set, the tracing is added in __system_property_set() instead of
__system_property_update() / __system_property_add() so we can record
control properties like ctl.*, sys.powerctl.*, etc.., which won't be
updated via the latter two functions.
Bug: 147275573
Test: atest CtsBionicTestCases
Test: adb shell perfetto -o /data/misc/perfetto-traces/test_trace -t 10s bionic
Test: adb shell perfetto -o /data/misc/perfetto-traces/test_trace -t 10s sysprop
Test: adb shell /data/benchmarktest64/bionic-benchmarks/bionic-benchmarks \
--benchmark_filter=BM_property --bionic_cpu=4, then compares the results
of property benchmarks before and after the change, didn't see
significant difference.
Change-Id: Id2b93acb2ce02b308c0e4889f836159151af3b46
Merged-In: Id2b93acb2ce02b308c0e4889f836159151af3b46
(cherry picked from commit 26970c3493)
Right now, when we read a system property, we first (assuming we've
already looked up the property's prop_info) read the property's serial
number; if we find that the low bit (the dirty bit) in the serial
number is set, we futex-wait for that serial number to become
non-dirty. By doing so, we spare readers from seeing partially-updated
property values if they race with the property service's non-atomic
memcpy to the property value slot. (The futex-wait here isn't
essential to the algorithm: spinning while dirty would suffice,
although it'd be somewhat less efficient.)
The problem with this approach is that readers can wait on the
property service process, potentially causing delays due to scheduling
variance. Property reads are not guaranteed to complete in finite time
right now.
This change makes property reads wait-free and ensures that they
complete in finite time in all cases. In the new approach, we prevent
value tearing by backing up each property we're about to modify and
directing readers to the backup copy if they try to read a property
with the dirty bit set.
(The wait freedom is limited to the case of readers racing against
*one* property update. A writer can still delay readers by rapidly
updating a property --- but after this change, readers can't hang due
to PID 1 scheduling delays.)
I considered adding explicit atomic access to short property values,
but between binary compatibility with the existing property database
and the need to carefully handle transitions of property values
between "short" (compatible with atomics) and "long" (incompatible
with atomics) length domains, I figured the complexity wasn't worth it
and that making property reads wait-free would be adequate.
Test: boots
Bug: 143561649
Change-Id: Ifd3108aedba5a4b157b66af6ca0a4ed084bd5982
Use <android-base/macros.h> instead where possible, and move the bionic
macros out of the way of the libbase ones. Yes, there are folks who manage
to end up with both included at once (thanks OpenGL!), and cleaning that
up doesn't seem nearly as practical as just making this change.
Bug: N/A
Test: builds
Change-Id: I23fc544f39d5addf81dc61471771a5438778895b
With the goal of disallowing exit time destructors, SystemProperties's
non-trivial destructor needs to be removed. This means replacing the
union hack with yet another hack as we don't want to allocate anything
despite relying on some polymorphism.
Bug: 73485611
Test: boot bullhead
Change-Id: I64223714c9b26c9724bfb8f3e2b0168e47b56bc8
We've been using #pragma once for new internal files, but let's be more bold.
Bug: N/A
Test: builds
Change-Id: I7e2ee2730043bd884f9571cdbd8b524043030c07
There were a bunch more unreasonable/incorrect ones, but these ones
seemed legit. Nothing very interesting, though.
Bug: N/A
Test: ran tests, benchmarks
Change-Id: If66971194d4a7b4bf6d0251bedb88e8cdc88a76f
Reinitializing system properties can result in crashes later in the
program, and is generally not recommended or even supported. This
change moves the actual logic for system properties into a class that
can be tested in isolation, without reinitializing the actual system
property area used in libc.
Bug: 62197783
Test: boot devices, ensure properties work
Test: system property unit tests and benchmarks
Change-Id: I9ae6e1b56c62f51a4d3fdb5b62b8926cef545649
