From 5ecaaa4eb7f210fcc5b2f6cd27b409f124bfd11e Mon Sep 17 00:00:00 2001
From: Benety Goh <benety@mongodb.com>
Date: Wed, 26 Aug 2015 22:01:13 -0400
Subject: Revert "SERVER-20052 yield when waiting/blocking for read committed"

This reverts commit 6fbd22f5f812885002b5d4cdd23a8bfec843ce82.
---
 src/mongo/db/db_raii.cpp | 80 +++++++++++++++++-------------------------------
 1 file changed, 28 insertions(+), 52 deletions(-)

(limited to 'src/mongo/db/db_raii.cpp')

diff --git a/src/mongo/db/db_raii.cpp b/src/mongo/db/db_raii.cpp
index 5a0c9f964bd..a987062b11b 100644
--- a/src/mongo/db/db_raii.cpp
+++ b/src/mongo/db/db_raii.cpp
@@ -38,7 +38,6 @@
 #include "mongo/db/repl/replication_coordinator_global.h"
 #include "mongo/db/stats/top.h"
 #include "mongo/s/d_state.h"
-#include "mongo/util/scopeguard.h"
 
 namespace mongo {
 
@@ -74,63 +73,40 @@ AutoGetCollectionForRead::AutoGetCollectionForRead(OperationContext* txn, const
 AutoGetCollectionForRead::AutoGetCollectionForRead(OperationContext* txn,
                                                    const NamespaceString& nss)
     : _txn(txn), _transaction(txn, MODE_IS), _autoColl(txn, nss, MODE_IS) {
-    {
-        auto curOp = CurOp::get(_txn);
-        stdx::lock_guard<Client> lk(*_txn->getClient());
+    // We have both the DB and collection locked, which the prerequisite to do a stable shard
+    // version check
+    ensureShardVersionOKOrThrow(_txn, nss.ns());
 
-        // TODO: OldClientContext legacy, needs to be removed
-        curOp->ensureStarted();
-        curOp->setNS_inlock(nss.ns());
-
-        // At this point, we are locked in shared mode for the database by the DB lock in the
-        // constructor, so it is safe to load the DB pointer.
-        if (_autoColl.getDb()) {
-            // TODO: OldClientContext legacy, needs to be removed
-            curOp->enter_inlock(nss.ns().c_str(), _autoColl.getDb()->getProfilingLevel());
-        }
-    }
+    auto curOp = CurOp::get(_txn);
+    stdx::lock_guard<Client> lk(*_txn->getClient());
 
-    // We have both the DB and collection locked, which is the prerequisite to do a stable shard
-    // version check, but we'd like to do the check after we have a satisfactory snapshot.
-    ON_BLOCK_EXIT([&]() { ensureShardVersionOKOrThrow(_txn, nss.ns()); });
+    // TODO: OldClientContext legacy, needs to be removed
+    curOp->ensureStarted();
+    curOp->setNS_inlock(nss.ns());
 
-    if (!getCollection()) {
-        return;
-    }
-    auto minSnapshot = getCollection()->getMinimumVisibleSnapshot();
-    if (!minSnapshot) {
-        return;
-    }
-    auto mySnapshot = _txn->recoveryUnit()->getMajorityCommittedSnapshot();
-    if (!mySnapshot) {
-        return;
-    }
-    if (mySnapshot > minSnapshot) {
-        return;
+    // At this point, we are locked in shared mode for the database by the DB lock in the
+    // constructor, so it is safe to load the DB pointer.
+    if (_autoColl.getDb()) {
+        // TODO: OldClientContext legacy, needs to be removed
+        curOp->enter_inlock(nss.ns().c_str(), _autoColl.getDb()->getProfilingLevel());
     }
 
-    // Save lock state for yielding.
-    Locker* locker = _txn->lockState();
-    Locker::LockSnapshot lockStateBackup;
-    massert(28795,
-            str::stream() << "Unable to yield to wait for readConcern=majority "
-            << "snapshot to be available for " << nss.ns(),
-            locker->saveLockStateAndUnlock(&lockStateBackup));
-    ON_BLOCK_EXIT([&]() { locker->restoreLockState(lockStateBackup); });
-
-    // Wait until a snapshot is available.
-    while (mySnapshot < minSnapshot) {
-        repl::ReplicationCoordinator::get(_txn)->waitForNewSnapshot(_txn);
-
-        Status status = _txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
-        uassert(28786,
-                "failed to set read from majority-committed snapshot",
-                status.isOK());
-        mySnapshot = _txn->recoveryUnit()->getMajorityCommittedSnapshot();
+    if (getCollection()) {
+        if (auto minSnapshot = getCollection()->getMinimumVisibleSnapshot()) {
+            if (auto mySnapshot = _txn->recoveryUnit()->getMajorityCommittedSnapshot()) {
+                while (mySnapshot < minSnapshot) {
+                    // Wait until a snapshot is available.
+                    repl::ReplicationCoordinator::get(_txn)->waitForNewSnapshot(_txn);
+
+                    Status status = _txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
+                    uassert(28786,
+                            "failed to set read from majority-committed snapshot",
+                            status.isOK());
+                    mySnapshot = _txn->recoveryUnit()->getMajorityCommittedSnapshot();
+                }
+            }
+        }
     }
-
-    stdx::lock_guard<Client> lk(*_txn->getClient());
-    CurOp::get(_txn)->yielded();
 }
 
 AutoGetCollectionForRead::~AutoGetCollectionForRead() {
-- 
cgit v1.2.1