Threads in the new ISO C Standard from 2011

More documents

Recommendations

Info

From the Linux Kernel Documentation rcu_dereference() typeof(p) rcu_dereference(p); Like rcu_assign_pointer(), rcu_dereference() must be implemented as a macro. The reader uses rcu_dereference() to fetch an RCU-protected pointer, which returns a value that may then be safely dereferenced. Note that rcu_deference() does not actually dereference the pointer, instead, it protects the pointer for later dereferencing. It also executes any needed memory-barrier instructions for a given CPU architecture. Currently, only Alpha needs memory barriers within rcu_dereference() -- on other CPUs, it compiles to nothing, not even a compiler directive. Jonas Skeppstedt (js@cs.lth.se) Lecture 6 2013 38 / 70
A Simplified Example Consider the following example code (also originally from Linux) list_t* head; int b; void insert(int a) { list_t* p = kmalloc(sizeof *p, GFP_KERNEL); } spin_lock(&m); p->a = 1; p->next = head; rcu_assign_pointer(head, p); spin_unlock(&m); void first(void) { list_t* q = rcu_dereference(head); } return q->a + b; The use of rcu_dereference() must be done within an rcu_read_lock() / rcu_read_unlock() — not seen in this example. Jonas Skeppstedt (js@cs.lth.se) Lecture 6 2013 39 / 70
Page 1 and 2: Threads in the new ISO C Standard f
Page 3 and 4: Atomic Objects Atomic objects are n
Page 5 and 6: Using Atomic Objects Members of an
Page 7 and 8: Lock Free Property To know whether
Page 9 and 10: Memory Order for Atomic Operations
Page 11 and 12: Answer: Yes The code may execute in
Page 13 and 14: Atomic Compare and Exchange There a
Page 15 and 16: Weak Compare and Exchange Functions
Page 17 and 18: Atomic Fetch and Modify Functions T
Page 19 and 20: Atomic Flag The atomic flag type an
Page 21 and 22: The C11 Memory Consistency Model fo
Page 23 and 24: Release and Acquire, and Consume Re
Page 25 and 26: Happens Before and Data Races We wi
Page 27 and 28: Sequenced Before The most common se
Page 29 and 30: An Example _Atomic int m; int u; //
Page 31 and 32: Dependences Dependences are intra-t
Page 33 and 34: Definition of Dependency in C11 A c
Page 35 and 36: Inter-Thread Happens Before An eval
Page 37: Read-Copy Update RCU is an alternat
Page 41 and 42: More Details About Dependences Reca
Page 43 and 44: Constant Propagation Example 2(3) T
Page 45 and 46: One More Data Dependency a = atomic
Page 47 and 48: Load and Reserve/Store Conditional
Page 49 and 50: Power Memory Barrier Instructions T
Page 51 and 52: lwsync Memory Barrier for Release O
Page 53 and 54: c;isync Memory Barrier for Load Acq
Page 55 and 56: Cumulative Ordering If the memory a
Page 57 and 58: Implementation on Power The followi
Page 59 and 60: Store Store relaxed st Store releas
Page 61 and 62: Acquire and Release a Spin Lock # a
Page 63 and 64: Initialization Function void call_o
Page 65 and 66: Mutex Options for mtx_init Function
Page 67 and 68: Condition Variable Functions int cn
Page 69 and 70: Thread Functions int thrd_create(th

Threads in the new ISO C Standard from 2011

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?