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[lldb] Implement coalescing of disjoint progress events (#84854)

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This implements coalescing of progress events using a timeout, as
discussed in the RFC on Discourse [1]. This PR consists of two commits
which, depending on the feedback, I may split up into two PRs. For now,
I think it's easier to review this as a whole.

1. The first commit introduces a new generic `Alarm` class. The class
lets you to schedule a function (callback) to be executed after a given
timeout expires. You can cancel and reset a callback before its
corresponding timeout expires. It achieves this with the help of a
worker thread that sleeps until the next timeout expires. The only
guarantee it provides is that your function is called no sooner than the
requested timeout. Because the callback is called directly from the
worker thread, a long running callback could potentially block the
worker thread. I intentionally kept the implementation as simple as
possible while addressing the needs for the `ProgressManager` use case.
If we want to rely on this somewhere else, we can reassess whether we
need to address those limitations.

2. The second commit uses the Alarm class to coalesce progress events.
To recap the Discourse discussion, when multiple progress events with
the same title execute in close succession, they get broadcast as one to
`eBroadcastBitProgressCategory`. The `ProgressManager` keeps track of
the in-flight progress events and when the refcount hits zero, the Alarm
class is used to schedule broadcasting the event. If a new progress
event comes in before the alarm fires, the alarm is reset (and the
process repeats when the new progress event ends). If no new event comes
in before the timeout expires, the progress event is broadcast.

[1]
https://discourse.llvm.org/t/rfc-improve-lldb-progress-reporting/75717/
This commit is contained in:
Jonas Devlieghere
2024-03-25 14:50:58 -07:00
parent 5e6e40fee3
commit 156c290746
4 changed files with 167 additions and 35 deletions
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14
lldb/source/API/SystemInitializerFull.cpp
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@@ -10,6 +10,7 @@
#include "lldb/API/SBCommandInterpreter.h"
#include "lldb/Core/Debugger.h"
#include "lldb/Core/PluginManager.h"
#include "lldb/Core/Progress.h"
#include "lldb/Host/Config.h"
#include "lldb/Host/Host.h"
#include "lldb/Initialization/SystemInitializerCommon.h"
@@ -57,6 +58,7 @@ llvm::Error SystemInitializerFull::Initialize() {
llvm::InitializeAllAsmPrinters();
llvm::InitializeAllTargetMCs();
llvm::InitializeAllDisassemblers();
// Initialize the command line parser in LLVM. This usually isn't necessary
// as we aren't dealing with command line options here, but otherwise some
// other code in Clang/LLVM might be tempted to call this function from a
@@ -65,10 +67,13 @@ llvm::Error SystemInitializerFull::Initialize() {
const char *arg0 = "lldb";
llvm::cl::ParseCommandLineOptions(1, &arg0);
// Initialize the progress manager.
ProgressManager::Initialize();
#define LLDB_PLUGIN(p) LLDB_PLUGIN_INITIALIZE(p);
#include "Plugins/Plugins.def"
// Scan for any system or user LLDB plug-ins
// Scan for any system or user LLDB plug-ins.
PluginManager::Initialize();
// The process settings need to know about installed plug-ins, so the
@@ -84,15 +89,18 @@ llvm::Error SystemInitializerFull::Initialize() {
void SystemInitializerFull::Terminate() {
Debugger::SettingsTerminate();
// Terminate plug-ins in core LLDB
// Terminate plug-ins in core LLDB.
ProcessTrace::Terminate();
// Terminate and unload and loaded system or user LLDB plug-ins
// Terminate and unload and loaded system or user LLDB plug-ins.
PluginManager::Terminate();
#define LLDB_PLUGIN(p) LLDB_PLUGIN_TERMINATE(p);
#include "Plugins/Plugins.def"
// Terminate the progress manager.
ProgressManager::Terminate();
// Now shutdown the common parts, in reverse order.
SystemInitializerCommon::Terminate();
}