auth: get rid of deadlocking channel passing scheme in simpleTokenTTL

[heyitsanthony]

Just use the mutex instead.

Fixes #7471

[xiang90]

LGTM. Is it easy to get a test covering the bad case?

/cc @davissp14 do you mind giving this a quick test?

[davissp14]

@xiang90 Sadly I am out tonight, but will be able to test tomorrow morning.

[xiang90]

lgtm

[mitake]

@heyitsanthony thanks a lot for the fix! The changes look good to me. But I could reproduce the test failure on my local env, too:

--- FAIL: TestCtlV3UserDelete (1.19s)
	ctl_v3_user_test.go:93: userDelTest #1: ctlV3User error (read /dev/ptmx: input/output error)
	ctl_v3_test.go:150: error closing etcd processes (exit status 2)
=== RUN   TestCtlV3UserPasswd
--- FAIL: TestCtlV3UserPasswd (0.69s)
	ctl_v3_user_test.go:116: userPasswdTest #1: ctlV3User error (read /dev/ptmx: input/output error)
	ctl_v3_test.go:150: error closing etcd processes (exit status 2)

I'll take a look at the test cases.

[davissp14]

Tested out the changes and wasn't able to reproduce the deadlock. Nice work!

[heyitsanthony]

@mitake the crash was caused by calling UserDelete when auth is disabled; the ttl keeper was nil so trying to acquire the lock in invalidateUser would crash it.

[mitake]

@heyitsanthony I see. lgtm after CIs can be passed, thanks!

[codecov-io]

Codecov Report

Merging #7492 into master will decrease coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #7492      +/-   ##
==========================================
- Coverage   70.73%   70.65%   -0.09%     
==========================================
  Files         245      245              
  Lines       21486    21487       +1     
==========================================
- Hits        15198    15181      -17     
- Misses       5156     5176      +20     
+ Partials     1132     1130       -2

Impacted Files	Coverage Δ
auth/simple_token.go	94.73% <100%> (+8.01%)	✅
pkg/adt/interval_tree.go	78.71% <0%> (-6.09%)	❌
lease/leasehttp/http.go	59.54% <0%> (-3.06%)	❌
pkg/netutil/netutil.go	77.94% <0%> (-2.95%)	❌
rafthttp/msgappv2_codec.go	69.56% <0%> (-1.74%)	❌
etcdserver/server.go	78.45% <0%> (-1.29%)	❌
etcdserver/v3_server.go	61.84% <0%> (-1.1%)	❌
raft/node.go	89.73% <0%> (-0.45%)	❌
rafthttp/transport.go	81.92% <0%> (ø)	✅
rafthttp/stream.go	89.7% <0%> (+0.66%)	✅
... and 6 more

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[davissp14]

Will this be added to 3.1.4?

[heyitsanthony]

@davissp14 yes, it's tagged for backporting