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From 6b7f87a557170164518d7c3b8e408304f2a9c1f4 Mon Sep 17 00:00:00 2001
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From: Thierry Bordaz <tbordaz@redhat.com>
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Date: Fri, 17 May 2019 14:31:45 +0200
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Subject: [PATCH] Ticket 50389 - ns-slapd craches while two threads are polling
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the same connection
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Bug Description:
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nspr IO is not multi-threaded safe.
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389-ds should not be in a situation where several threads are polling
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a same connection at the same time.
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The scenario is a worker send back an operation result at the same time
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another worker wants to read an incoming request.
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Fix Description:
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The fix consist in synchonizing polling with c_pdumutex.
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The thread that sends data (flush_ber) hold c_pdumutex.
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The thread that reads the data does a non blocking read. It then
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enforce ioblocktimeout with iteration of poll.
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The reading thread must hold c_pdumutex during poll to synchronize
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with the reader thread.
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The reading thread must poll with a small timeout
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(CONN_TURBO_TIMEOUT_INTERVAL). In order to not block
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the thread that send back data, the fix reduces the delay to 0.1s.
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https://pagure.io/389-ds-base/issue/50389
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Reviewed by: Mark Reynolds, Matus Honek, William Brown
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Platforms tested: F28
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Flag Day: no
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Doc impact: no
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(cherry picked from commit 2886ba77f664e4734a7ddfe4146f229caca49ce4)
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---
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ldap/servers/slapd/connection.c | 5 ++++-
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ldap/servers/slapd/daemon.c | 2 ++
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2 files changed, 6 insertions(+), 1 deletion(-)
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diff --git a/ldap/servers/slapd/connection.c b/ldap/servers/slapd/connection.c
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index 188383b97..945602f20 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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@@ -932,7 +932,8 @@ connection_free_private_buffer(Connection *conn)
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#define CONN_DONE 3
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#define CONN_TIMEDOUT 4
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-#define CONN_TURBO_TIMEOUT_INTERVAL 1000 /* milliseconds */
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+#define CONN_TURBO_TIMEOUT_INTERVAL 100 /* milliseconds */
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+#define CONN_TURBO_TIMEOUT_MAXIMUM 5 /* attempts * interval IE 2000ms with 400 * 5 */
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#define CONN_TURBO_CHECK_INTERVAL 5 /* seconds */
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#define CONN_TURBO_PERCENTILE 50 /* proportion of threads allowed to be in turbo mode */
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#define CONN_TURBO_HYSTERESIS 0 /* avoid flip flopping in and out of turbo mode */
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@@ -1207,7 +1208,9 @@ connection_read_operation(Connection *conn, Operation *op, ber_tag_t *tag, int *
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pr_pd.fd = (PRFileDesc *)conn->c_prfd;
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pr_pd.in_flags = PR_POLL_READ;
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pr_pd.out_flags = 0;
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+ PR_Lock(conn->c_pdumutex);
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ret = PR_Poll(&pr_pd, 1, timeout);
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+ PR_Unlock(conn->c_pdumutex);
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waits_done++;
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/* Did we time out ? */
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if (0 == ret) {
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diff --git a/ldap/servers/slapd/daemon.c b/ldap/servers/slapd/daemon.c
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index c77e1f15c..4841a8a5c 100644
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--- a/ldap/servers/slapd/daemon.c
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+++ b/ldap/servers/slapd/daemon.c
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@@ -1943,6 +1943,8 @@ ns_handle_pr_read_ready(struct ns_job_t *job)
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* or something goes seriously wrong. Otherwise, return 0.
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* If -1 is returned, PR_GetError() explains why.
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* Revision: handle changed to void * to allow 64bit support
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+ *
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+ * Caller (flush_ber) must hold conn->c_pdumutex
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*/
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static int
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slapd_poll(void *handle, int output)
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--
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2.17.2
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