tree 5172c02b7957c07ef22971eab1ce5b03e4dbd44b
parent 5cfa93810a407da48fe72b9e11df6e2bb7f17d9b
author Primiano Tucci <primiano@google.com> 1538386869 +0100
committer Primiano Tucci <primiano@google.com> 1538386869 +0100

Introduce support for deferred start (fast triggering)

This CL introduces new Setup methods to both the
producer and consumer API. The API changes are designed
to be backwards compatible with the prior versions of
Android.

From the producer viewpoint: each data source now sees a
SetupDataSource() method before the StartDataSource() method.
The data source instance id and config is identical. This
gives the data source a chance to setup itself before actually
starting.

From the consumer viewpoint:
A new "deferred_start" field is added to the TraceConfig.
When deferred_start is true, the EnableTracing method
brings up all the tracing harness and calls the
SetupDataSource() methods on the producers, but doesn't
start them. Data sources are started only when calling
StartDataSource().

Note that in this CL, the ftrace data source doesn't
deal yet with the split Setup/Start phases and starts
directly upon creation. This will be fixed in a separate
CL.

Bug: 116547201
Change-Id: I2ab22c7f8ee2388f8158df733dddeef9dc9c0143