diff options
Diffstat (limited to 'src/runtime/trace.go')
| -rw-r--r-- | src/runtime/trace.go | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/src/runtime/trace.go b/src/runtime/trace.go index 7130e2c136..0fdc829f71 100644 --- a/src/runtime/trace.go +++ b/src/runtime/trace.go @@ -13,17 +13,17 @@ // ## Design // // The basic idea behind the the execution tracer is to have per-M buffers that -// trace data may be written into. Each M maintains a seqlock indicating whether +// trace data may be written into. Each M maintains a write flag indicating whether // its trace buffer is currently in use. // // Tracing is initiated by StartTrace, and proceeds in "generations," with each // generation being marked by a call to traceAdvance, to advance to the next // generation. Generations are a global synchronization point for trace data, // and we proceed to a new generation by moving forward trace.gen. Each M reads -// trace.gen under its own seqlock to determine which generation it is writing +// trace.gen under its own write flag to determine which generation it is writing // trace data for. To this end, each M has 2 slots for buffers: one slot for the // previous generation, one slot for the current one. It uses tl.gen to select -// which buffer slot to write to. Simultaneously, traceAdvance uses the seqlock +// which buffer slot to write to. Simultaneously, traceAdvance uses the write flag // to determine whether every thread is guaranteed to observe an updated // trace.gen. Once it is sure, it may then flush any buffers that are left over // from the previous generation safely, since it knows the Ms will not mutate @@ -43,7 +43,7 @@ // appear in pairs: one for the previous generation, and one for the current one. // Like the per-M buffers, which of the two is written to is selected using trace.gen, // and anything managed this way must similarly be mutated only in traceAdvance or -// under the M's seqlock. +// under the M's write flag. // // Trace events themselves are simple. They consist of a single byte for the event type, // followed by zero or more LEB128-encoded unsigned varints. They are decoded using @@ -629,7 +629,7 @@ func traceAdvance(stopTrace bool) { // while they're still on that list. Removal from sched.freem is serialized with // this snapshot, so either we'll capture an m on sched.freem and race with // the removal to flush its buffers (resolved by traceThreadDestroy acquiring - // the thread's seqlock, which one of us must win, so at least its old gen buffer + // the thread's write flag, which one of us must win, so at least its old gen buffer // will be flushed in time for the new generation) or it will have flushed its // buffers before we snapshotted it to begin with. lock(&sched.lock) @@ -645,7 +645,7 @@ func traceAdvance(stopTrace bool) { // Iterate over our snapshot, flushing every buffer until we're done. // - // Because trace writers read the generation while the seqlock is + // Because trace writers read the generation while the write flag is // held, we can be certain that when there are no writers there are // also no stale generation values left. Therefore, it's safe to flush // any buffers that remain in that generation's slot. @@ -658,7 +658,7 @@ func traceAdvance(stopTrace bool) { for mToFlush != nil { prev := &mToFlush for mp := *prev; mp != nil; { - if mp.trace.seqlock.Load()%2 != 0 { + if mp.trace.writing.Load() { // The M is writing. Come back to it later. prev = &mp.trace.link mp = mp.trace.link |