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runtime: convert semaRoot.nwait to atomic type
For #53821 Change-Id: I686fe81268f70acc6a4c3e6b1d3ed0e07bb0d61c Reviewed-on: https://go-review.googlesource.com/c/go/+/425775 Run-TryBot: xie cui <523516579@qq.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com> Auto-Submit: Michael Knyszek <mknyszek@google.com> Run-TryBot: Michael Pratt <mpratt@google.com>
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@ -1164,7 +1164,7 @@ var Semrelease1 = semrelease1
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func SemNwait(addr *uint32) uint32 {
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root := semtable.rootFor(addr)
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return atomic.Load(&root.nwait)
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return root.nwait.Load()
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}
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const SemTableSize = semTabSize
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@ -40,7 +40,7 @@ import (
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type semaRoot struct {
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lock mutex
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treap *sudog // root of balanced tree of unique waiters.
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nwait uint32 // Number of waiters. Read w/o the lock.
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nwait atomic.Uint32 // Number of waiters. Read w/o the lock.
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}
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var semtable semTable
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@ -137,10 +137,10 @@ func semacquire1(addr *uint32, lifo bool, profile semaProfileFlags, skipframes i
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for {
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lockWithRank(&root.lock, lockRankRoot)
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// Add ourselves to nwait to disable "easy case" in semrelease.
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atomic.Xadd(&root.nwait, 1)
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root.nwait.Add(1)
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// Check cansemacquire to avoid missed wakeup.
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if cansemacquire(addr) {
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atomic.Xadd(&root.nwait, -1)
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root.nwait.Add(-1)
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unlock(&root.lock)
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break
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}
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@ -169,13 +169,13 @@ func semrelease1(addr *uint32, handoff bool, skipframes int) {
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// Easy case: no waiters?
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// This check must happen after the xadd, to avoid a missed wakeup
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// (see loop in semacquire).
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if atomic.Load(&root.nwait) == 0 {
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if root.nwait.Load() == 0 {
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return
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}
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// Harder case: search for a waiter and wake it.
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lockWithRank(&root.lock, lockRankRoot)
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if atomic.Load(&root.nwait) == 0 {
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if root.nwait.Load() == 0 {
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// The count is already consumed by another goroutine,
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// so no need to wake up another goroutine.
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unlock(&root.lock)
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@ -183,7 +183,7 @@ func semrelease1(addr *uint32, handoff bool, skipframes int) {
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}
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s, t0 := root.dequeue(addr)
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if s != nil {
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atomic.Xadd(&root.nwait, -1)
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root.nwait.Add(-1)
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}
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unlock(&root.lock)
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if s != nil { // May be slow or even yield, so unlock first
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