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fix missing initial sync.RWMutex #2305

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merged 3 commits into from Mar 27, 2020
Merged

fix missing initial sync.RWMutex #2305

merged 3 commits into from Mar 27, 2020

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appleboy
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@appleboy appleboy commented Mar 27, 2020

fix #2301

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
@appleboy appleboy added this to the 1.6.2 milestone Mar 27, 2020
@appleboy appleboy requested a review from thinkerou Mar 27, 2020
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@codecov codecov bot commented Mar 27, 2020

Codecov Report

Merging #2305 into master will decrease coverage by 0.08%.
The diff coverage is 50.00%.

Impacted file tree graph

@@            Coverage Diff             @@
##           master    #2305      +/-   ##
==========================================
- Coverage   98.47%   98.39%   -0.09%     
==========================================
  Files          41       41              
  Lines        2300     2304       +4     
==========================================
+ Hits         2265     2267       +2     
- Misses         20       21       +1     
- Partials       15       16       +1     
Impacted Files Coverage Δ
context.go 97.65% <50.00%> (-0.41%) ⬇️

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Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
@appleboy appleboy added the bug label Mar 27, 2020
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@thinkerou thinkerou left a comment

LGTM

@appleboy appleboy merged commit 298ebca into master Mar 27, 2020
2 of 4 checks passed
@appleboy appleboy deleted the bugs2 branch Mar 27, 2020
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@bbiao bbiao commented Mar 27, 2020

If two go routine concurrently access a context which has no mutex, maybe lead to problem.

        if c.KeysMutex == nil {
		c.KeysMutex = &sync.RWMutex{}
	}
......
	c.KeysMutex.RLock()
	value, exists = c.Keys[key]
	c.KeysMutex.RUnlock()

If two go routine both check c.KeysMutex == nil,and get a true result, one of them create a new sync.RWMutext and run to c.KeysMutex.RLock(), and another create a new sync.RWMutext, then
mutex in c.KeysMutex.RUnlock() maybe different from the one used in c.KeysMutex.RLock()

@@ -228,6 +228,10 @@ func (c *Context) Error(err error) *Error {
// Set is used to store a new key/value pair exclusively for this context.
// It also lazy initializes c.Keys if it was not used previously.
func (c *Context) Set(key string, value interface{}) {
if c.KeysMutex == nil {
c.KeysMutex = &sync.RWMutex{}
}
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@felix-h felix-h Mar 30, 2020

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@appleboy @thinkerou Isn't the mutex creation still a race condition? For two threads that are both calling "Set" at the same time, the mutex could get created twice -- once for each thread. What about using "sync.once" here?

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@appleboy appleboy Mar 30, 2020

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Good catch.

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@appleboy appleboy May 3, 2020

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@felix-h fix in #2351

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@appleboy appleboy commented May 3, 2020

The PR trigger the performance issue in #2350

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4 participants