acquire lock before accessing shared redis context

[anilkpandey]

Multiple threads in syncd access ASIC_DB through the same redis context. g_mutex is used to synchronize the access as hiredis is not thread safe.
Function try_translate_vid_to_rid(), which accesses ASIC_DB was being called unprotected. This caused one of the threads to stuck on redisBufferRead().

(gdb) bt
#0 0x00007f15301cd22d in read () from /lib/x86_64-linux-gnu/libpthread.so.0
#1 0x00007f1537ebf6a2 in read (__nbytes=16384, __buf=0x7f152d6b0910,
__fd=) at /usr/include/x86_64-linux-gnu/bits/unistd.h:44
#2 redisBufferRead (c=0x55c450ffdde0) at hiredis.c:802
#3 0x00007f1537ebf9a0 in redisGetReply (c=0x55c450ffdde0,
reply=reply@entry=0x7f152d6b4a00) at hiredis.c:888
#4 0x00007f1537c612d0 in swss::RedisReply::RedisReply (this=0x7f152d6b4a00,
db=0x55c451001e80, command=...) at redisreply.cpp:33
#5 0x00007f1537c614c2 in swss::RedisReply::RedisReply (this=0x7f152d6b4a00,
db=, command=..., expectedType=3) at redisreply.cpp:45
#6 0x00007f1537c7efba in swss::RedisClient::hset (this=0x55c450ffd510,
key="ASIC_STATE:SAI_OBJECT_TYPE_FDB_ENTRY:{"bvid":"oid:0x26000000000e17","mac":"3C:2C:99:8B:35:BC","switch_id":"oid:0x21", '0' <repeats 12 times>, ""}", field="SAI_FDB_ENTRY_ATTR_BRIDGE_PORT_ID",
value="oid:0x3a00000000104d") at redisclient.cpp:56

[kcudnik]

good catch, this is due to move processFlexCounterEvent to be executed to separate theread
which is result of making workaround for postpone counters subscribe which should be synchronous on first place

[lguohan]

@anilkpandey, can you resolve the conflict?

[anilkpandey]

@anilkpandey, can you resolve the conflict?

I am not able to, may be because I don't have write access.

[prsunny]

You can merge/rebase from master and push to this PR. You don't have to use the resolve button above.

[prsunny]

Looks like the editor added a lot of tab spaces. Kindly revert the space changes and recommit.

[anilkpandey]

Looks like the editor added a lot of tab spaces. Kindly revert the space changes and recommit.

Done