1. brpop last key index, thus checking all keys for slots.
2. Memory leak in clusterRedirectBlockedClientIfNeeded.
3. Remove while loop in clusterRedirectBlockedClientIfNeeded.
This avoids Helgrind complaining, but we are actually not using
atomicGet() to get the unixtime value for now: too many places where it
is used and given tha time_t is word-sized it should be safe in all the
archs we support as it is.
On the other hand, Helgrind, when Redis is compiled with "make helgrind"
in order to force the __sync macros, will detect the write in
updateCachedTime() as a read (because atomic functions are used) and
will not complain about races.
This commit also includes minor refactoring of mutex initializations and
a "helgrind" target in the Makefile.
The __sync builtin can be correctly detected by Helgrind so to force it
is useful for testing. The API in the INFO output can be useful for
debugging after problems are reported.
Instead of giving the module background operations just a small time to
run in the beforeSleep() function, we can have the lock released for all
the time we are blocked in the multiplexing syscall.
Experimentally verified that it can trigger the issue reverting the fix.
At least on my system... Being the bug time/backlog dependant, it is
very hard to tell if this test will be able to trigger the problem
consistently, however even if it triggers the problem once in a while,
we'll see it in the CI environment at http://ci.redis.io.
The master client cleanup was incomplete: resetClient() was missing and
the output buffer of the client was not reset, so pending commands
related to the previous connection could be still sent.
The first problem caused the client argument vector to be, at times,
half populated, so that when the correct replication stream arrived the
protcol got mixed to the arugments creating invalid commands that nobody
called.
Thanks to @yangsiran for also investigating this problem, after
already providing important design / implementation hints for the
original PSYNC2 issues (see referenced Github issue).
Note that this commit adds a new function to the list library of Redis
in order to be able to reset a list without destroying it.
Related to issue #3899.
