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    Concurrency, Synchronization and Deadlocks Short Notes for GATE CS

    Concurrency, Synchronization and Deadlocks short notes for GATE CS: 12 study cards covering concepts, formulas, shortcuts and exam traps, plus solved practice

    concurrency synchronization and deadlocks short notes

    Formula matrix

    2 threads, & atomic statements, no cross-constraints.
    threads, statements each, no cross-constraints.
    2 threads, Thread 1's 1st statement fixed at position 1.
    Load Modify Store
    High-level x = x + 1 without explicit atomicity.
    Global vs Local
    Global: single address. Local: independent stack frame per thread.
    Reachability
    Reverse-engineered precedence graph must be acyclic.

    If you see this, do this

    Stem TriggerFirst Move
    "lists all possible combinations"Enumerate valid interleavings preserving intra-thread order.
    "each statement is atomic"Treat each line as indivisible; no load/modify/store splits.
    int local = 0 inside functionIsolate variable; each thread gets independent copy.
    "IMPOSSIBLE to achieve"Reverse-engineer target state; check for cyclic precedence.
    "first statement of Thread X is absolute first"Fix position 1; count interleavings of remaining slots.
    x = x + 1 (no atomicity keyword)Decompose to Load, Modify, Store; check for context switches.
    static int x inside functionTreat as global shared state (data segment), not thread-local.

    Traps and invariants

    Assuming x = x + 1 is atomic. Check: Translate to Load/Modify/Store. If context switch can occur between steps, it is non-atomic.
    Counting interleavings violating intra-thread order. Check: Verify strictly precedes for every thread in the proposed sequence.
    Treating identically named local variables as shared. Check: Check declaration scope. Inside function = independent stack frames per thread.
    Accepting reverse-engineered states with cyclic dependencies. Check: Draw directed edges for required precedence. If a cycle forms, state is impossible.

    9 more cards in this chapter

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    Concurrency, Synchronization and Deadlocks Short Notes for GATE CS

    Concurrency, Synchronization and Deadlocks short notes for GATE CS: 12 study cards covering concepts, formulas, shortcuts and exam traps, plus solved practice questions.

    Formula matrix

    2 threads, & atomic statements, no cross-constraints.
    threads, statements each, no cross-constraints.
    2 threads, Thread 1's 1st statement fixed at position 1.
    Load Modify Store
    High-level x = x + 1 without explicit atomicity.
    Global vs Local
    Global: single address. Local: independent stack frame per thread.
    Reachability
    Reverse-engineered precedence graph must be acyclic.

    If you see this, do this

    Stem TriggerFirst Move
    "lists all possible combinations"Enumerate valid interleavings preserving intra-thread order.
    "each statement is atomic"Treat each line as indivisible; no load/modify/store splits.
    int local = 0 inside functionIsolate variable; each thread gets independent copy.
    "IMPOSSIBLE to achieve"Reverse-engineer target state; check for cyclic precedence.
    "first statement of Thread X is absolute first"Fix position 1; count interleavings of remaining slots.
    x = x + 1 (no atomicity keyword)Decompose to Load, Modify, Store; check for context switches.
    static int x inside functionTreat as global shared state (data segment), not thread-local.

    Traps and invariants

    Assuming x = x + 1 is atomic. Check: Translate to Load/Modify/Store. If context switch can occur between steps, it is non-atomic.
    Counting interleavings violating intra-thread order. Check: Verify strictly precedes for every thread in the proposed sequence.
    Treating identically named local variables as shared. Check: Check declaration scope. Inside function = independent stack frames per thread.
    Accepting reverse-engineered states with cyclic dependencies. Check: Draw directed edges for required precedence. If a cycle forms, state is impossible.

    Recall check

    More short notes in this unit