f838fa820f
This PR introduces a new `ThreadPlanSingleThreadTimeout` that will be used to address potential deadlock during single-thread stepping. While debugging a target with a non-trivial number of threads (around 5000 threads in one example target), we noticed that a simple step over can take as long as 10 seconds. Enabling single-thread stepping mode significantly reduces the stepping time to around 3 seconds. However, this can introduce deadlock if we try to step over a method that depends on other threads to release a lock. To address this issue, we introduce a new `ThreadPlanSingleThreadTimeout` that can be controlled by the `target.process.thread.single-thread-plan-timeout` setting during single-thread stepping mode. The concept involves counting the elapsed time since the last internal stop to detect overall stepping progress. Once a timeout occurs, we assume the target is not making progress due to a potential deadlock, as mentioned above. We then send a new async interrupt, resume all threads, and `ThreadPlanSingleThreadTimeout` completes its task. To support this design, the major changes made in this PR are: 1. `ThreadPlanSingleThreadTimeout` is popped during every internal stop and reset (re-pushed) to the top of the stack (as a leaf node) during resume. This is achieved by always returning `true` from `ThreadPlanSingleThreadTimeout::DoPlanExplainsStop()` and `ThreadPlanSingleThreadTimeout::MischiefManaged()`. 2. A new thread-specific async interrupt stop is introduced, which can be detected/consumed by `ThreadPlanSingleThreadTimeout`. 3. The clearing of branch breakpoints in the range thread plan has been moved from `DoPlanExplainsStop()` to `ShouldStop()`, as it is not guaranteed that it will be called. The detailed design is discussed in the RFC below: [https://discourse.llvm.org/t/improve-single-thread-stepping/74599](https://discourse.llvm.org/t/improve-single-thread-stepping/74599) --------- Co-authored-by: jeffreytan81 <jeffreytan@fb.com>
103 lines
4.0 KiB
C++
103 lines
4.0 KiB
C++
//===-- ThreadPlanStepRange.h -----------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLDB_TARGET_THREADPLANSTEPRANGE_H
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#define LLDB_TARGET_THREADPLANSTEPRANGE_H
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#include "lldb/Core/AddressRange.h"
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#include "lldb/Target/StackID.h"
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#include "lldb/Target/Thread.h"
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#include "lldb/Target/ThreadPlan.h"
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#include "lldb/Target/ThreadPlanShouldStopHere.h"
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namespace lldb_private {
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class ThreadPlanStepRange : public ThreadPlan {
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public:
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ThreadPlanStepRange(ThreadPlanKind kind, const char *name, Thread &thread,
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const AddressRange &range,
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const SymbolContext &addr_context,
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lldb::RunMode stop_others,
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bool given_ranges_only = false);
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~ThreadPlanStepRange() override;
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void GetDescription(Stream *s, lldb::DescriptionLevel level) override = 0;
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bool ValidatePlan(Stream *error) override;
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bool ShouldStop(Event *event_ptr) override = 0;
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Vote ShouldReportStop(Event *event_ptr) override;
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bool StopOthers() override;
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lldb::StateType GetPlanRunState() override;
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bool WillStop() override;
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bool MischiefManaged() override;
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void DidPush() override;
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bool IsPlanStale() override;
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void AddRange(const AddressRange &new_range);
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protected:
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bool InRange();
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lldb::FrameComparison CompareCurrentFrameToStartFrame();
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bool InSymbol();
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void DumpRanges(Stream *s);
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Disassembler *GetDisassembler();
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InstructionList *GetInstructionsForAddress(lldb::addr_t addr,
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size_t &range_index,
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size_t &insn_offset);
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// Pushes a plan to proceed through the next section of instructions in the
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// range - usually just a RunToAddress plan to run to the next branch.
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// Returns true if it pushed such a plan. If there was no available 'quick
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// run' plan, then just single step.
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bool SetNextBranchBreakpoint();
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// Whether the input stop info is caused by the next branch breakpoint.
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// Note: this does not check if branch breakpoint site is shared by other
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// breakpoints or not.
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bool IsNextBranchBreakpointStop(lldb::StopInfoSP stop_info_sp);
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void ClearNextBranchBreakpoint();
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void ClearNextBranchBreakpointExplainedStop();
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bool NextRangeBreakpointExplainsStop(lldb::StopInfoSP stop_info_sp);
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SymbolContext m_addr_context;
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std::vector<AddressRange> m_address_ranges;
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lldb::RunMode m_stop_others;
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StackID m_stack_id; // Use the stack ID so we can tell step out from step in.
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StackID m_parent_stack_id; // Use the parent stack ID so we can identify tail
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// calls and the like.
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bool m_no_more_plans; // Need this one so we can tell if we stepped into a
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// call,
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// but can't continue, in which case we are done.
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bool m_first_run_event; // We want to broadcast only one running event, our
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// first.
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lldb::BreakpointSP m_next_branch_bp_sp;
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bool m_use_fast_step;
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bool m_given_ranges_only;
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bool m_found_calls = false; // When we set the next branch breakpoint for
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// step over, we now extend them past call insns
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// that directly return. But if we do that we
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// need to run all threads, or we might cause
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// deadlocks. This tells us whether we found
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// any calls in setting the next branch breakpoint.
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private:
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std::vector<lldb::DisassemblerSP> m_instruction_ranges;
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ThreadPlanStepRange(const ThreadPlanStepRange &) = delete;
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const ThreadPlanStepRange &operator=(const ThreadPlanStepRange &) = delete;
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};
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} // namespace lldb_private
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#endif // LLDB_TARGET_THREADPLANSTEPRANGE_H
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