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From 2136ba8dd18e72bfbe037517c10187bfe695628f Mon Sep 17 00:00:00 2001
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From: Thierry Bordaz <tbordaz@redhat.com>
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Date: Thu, 24 May 2018 15:36:34 +0200
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Subject: [PATCH] Ticket 49768 - Under network intensive load persistent search
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can erronously decrease connection refcnt
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Bug Description:
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If a connection enters in turbo mode (because of high traffic) or
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a worker reads several requests in the read buffer (more_data), the thread
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keeps processing connection.
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In that condition it should not decrease the refcnt.
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In case the operation is a persistent search, it decreases systematically
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the refcnt.
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So refcnt can become lower than the actual number of threads active on the connection.
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Most of the time it can create messages like
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Attempt to release connection that is not acquired
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In some rare case, if the a connection is out of the active list but a remaining thread
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tries to remove it again it can lead to a crash
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Fix Description:
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The fix consist, when processing a PS, to decrease the refcnt at the condition
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the connection is not in turbo mode or in more_data.
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https://pagure.io/389-ds-base/issue/49768
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Reviewed by: Mark Reynolds
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Platforms tested: F26
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Flag Day: no
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Doc impact: no
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---
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ldap/servers/slapd/connection.c | 14 +++++++++++---
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1 file changed, 11 insertions(+), 3 deletions(-)
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diff --git a/ldap/servers/slapd/connection.c b/ldap/servers/slapd/connection.c
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index c54e7c26c..1dbb49f06 100644
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--- a/ldap/servers/slapd/connection.c
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+++ b/ldap/servers/slapd/connection.c
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@@ -1811,9 +1811,17 @@ connection_threadmain()
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slapi_counter_increment(ops_completed);
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/* If this op isn't a persistent search, remove it */
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if (op->o_flags & OP_FLAG_PS) {
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- PR_EnterMonitor(conn->c_mutex);
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- connection_release_nolock(conn); /* psearch acquires ref to conn - release this one now */
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- PR_ExitMonitor(conn->c_mutex);
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+ /* Release the connection (i.e. decrease refcnt) at the condition
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+ * this thread will not loop on it.
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+ * If we are in turbo mode (dedicated to that connection) or
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+ * more_data (continue reading buffered req) this thread
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+ * continues to hold the connection
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+ */
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+ if (!thread_turbo_flag && !more_data) {
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+ PR_EnterMonitor(conn->c_mutex);
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+ connection_release_nolock(conn); /* psearch acquires ref to conn - release this one now */
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+ PR_ExitMonitor(conn->c_mutex);
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+ }
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/* ps_add makes a shallow copy of the pb - so we
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* can't free it or init it here - just set operation to NULL.
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* ps_send_results will call connection_remove_operation_ext to free it
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--
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2.17.1
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