Port a fix from FRR community (#3614)

Author: sudhanshukumar22 <sudhanshu.kumar@broadcom.com>
Date:   Tue Oct 16 12:33:20 2019 -0700
     39c93f379a
     If we have a case where have created a fd for i/o and we have removed the
     handling thread but still have the fd in the poll data structure, there
     existed a case where we would get the handle this fd return from poll but we
     would immediately do nothing with it because we didn't have a thread to hand
     the event to.

     This leads to an infinite loop.  Prevent the infinite loop
    from happening and log the problem.
Signed-off-by: Preetham Singh (preetham.singh@broadcom.com)

src/sonic-frr/patch/0007-prevent-dead-fd-poll-data-port-fix-from-frr.patch

@@ -0,0 +1,107 @@
+From e4225086634fb7ae7fa762f3a45af6ad39e78641 Mon Sep 17 00:00:00 2001
+From: sudhanshukumar22 <sudhanshu.kumar@broadcom.com>
+Date: Tue, 15 Oct 2019 02:17:00 -0700
+Subject: [PATCH] Port a fix from FRR community 
+ https://github.com/donaldsharp/frr/commit/39c93f379a5b57c56739a339ad75ec06e30daef3
+  If we have a case where have created a fd for i/o and we have removed the 
+ handling thread but still have the fd in the poll data structure, there 
+ existed a case where we would get the handle this fd return from poll but we 
+ would immediately do nothing with it because we didn't have a thread to hand 
+ the event to.
+
+This leads to an infinite loop.  Prevent the infinite loop
+from happening and log the problem.
+---
+ lib/lib_errors.c |  6 ++++++
+ lib/lib_errors.h |  1 +
+ lib/thread.c     | 25 ++++++++++++++++++-------
+ 3 files changed, 25 insertions(+), 7 deletions(-)
+
+diff --git a/lib/lib_errors.c b/lib/lib_errors.c
+index b6c764d87..033f27e58 100644
+--- a/lib/lib_errors.c
++++ b/lib/lib_errors.c
+@@ -50,6 +50,12 @@ static struct log_ref ferr_lib_warn[] = {
+ 		.description = "The Event subsystem has detected a slow process, this typically indicates that FRR is having trouble completing work in a timely manner.  This can be either a misconfiguration, bug, or some combination therof.",
+ 		.suggestion = "Gather log data and open an Issue",
+ 	},
++	{
++        	.code = EC_LIB_NO_THREAD,
++        	.title = "The Event subsystem has detected an internal FD problem",
++        	.description = "The Event subsystem has detected a file descriptor read/write event without an associated handling function.  This is a bug, please collect log data and open an issue.",
++        	.suggestion = "Gather log data and open an Issue",
++    	},
+ 	{
+ 		.code = EC_LIB_RMAP_RECURSION_LIMIT,
+ 		.title = "Reached the Route-Map Recursion Limit",
+diff --git a/lib/lib_errors.h b/lib/lib_errors.h
+index 39b39fb06..996a16ba9 100644
+--- a/lib/lib_errors.h
++++ b/lib/lib_errors.h
+@@ -45,6 +45,7 @@ enum lib_log_refs {
+ 	EC_LIB_STREAM,
+ 	EC_LIB_LINUX_NS,
+ 	EC_LIB_SLOW_THREAD,
++	EC_LIB_NO_THREAD,
+ 	EC_LIB_RMAP_RECURSION_LIMIT,
+ 	EC_LIB_BACKUP_CONFIG,
+ 	EC_LIB_VRF_LENGTH,
+diff --git a/lib/thread.c b/lib/thread.c
+index 5ca859a74..82708557d 100644
+--- a/lib/thread.c
++++ b/lib/thread.c
+@@ -1235,12 +1235,26 @@ static struct thread *thread_run(struct thread_master *m, struct thread *thread,
+ }
+ 
+ static int thread_process_io_helper(struct thread_master *m,
+-				    struct thread *thread, short state, int pos)
++				    struct thread *thread, short state, short actual_state, int pos)
+ {
+ 	struct thread **thread_array;
+ 
+-	if (!thread)
++	/*
++	 * If another pthread scheduled this file descriptor for this event
++	 * we're responding to, no problem, we're getting to it now.
++	 * Additionally if !thread if we don't clear this now we'll
++	 * infinaloop( which sucks )
++	 */
++	m->handler.pfds[pos].events &= ~(state);
++
++	if (!thread) {
++		if ((actual_state & (POLLHUP | POLLIN)) != POLLHUP)
++			flog_err( EC_LIB_NO_THREAD,
++				  "Attempting to process an I/O event but for fd: %d(%d) no thread to handle this!\n",
++				  m->handler.pfds[pos].fd, actual_state);
+ 		return 0;
++	}
++
+ 
+ 	if (thread->type == THREAD_READ)
+ 		thread_array = m->read;
+@@ -1250,9 +1264,6 @@ static int thread_process_io_helper(struct thread_master *m,
+ 	thread_array[thread->u.fd] = NULL;
+ 	thread_list_add_tail(&m->ready, thread);
+ 	thread->type = THREAD_READY;
+-	/* if another pthread scheduled this file descriptor for the event we're
+-	 * responding to, no problem; we're getting to it now */
+-	thread->master->handler.pfds[pos].events &= ~(state);
+ 	return 1;
+ }
+ 
+@@ -1290,10 +1301,10 @@ static void thread_process_io(struct thread_master *m, unsigned int num)
+ 		 * should still be a valid index into the master's pfds. */
+ 		if (pfds[i].revents & (POLLIN | POLLHUP))
+ 			thread_process_io_helper(m, m->read[pfds[i].fd], POLLIN,
+-						 i);
++						 pfds[i].revents,i);
+ 		if (pfds[i].revents & POLLOUT)
+ 			thread_process_io_helper(m, m->write[pfds[i].fd],
+-						 POLLOUT, i);
++						 POLLOUT, pfds[i].revents, i);
+ 
+ 		/* if one of our file descriptors is garbage, remove the same
+ 		 * from
+-- 
+2.18.0
+

src/sonic-frr/patch/series

@@ -3,3 +3,4 @@
 0004-Allow-BGP-attr-NEXT_HOP-to-be-0.0.0.0-due-to-allevia.patch
 0005-Support-VRF.patch
 0006-changes-for-making-snmp-socket-non-blocking.patch
+0007-prevent-dead-fd-poll-data-port-fix-from-frr.patch