Any advice on tracking down the cause of "worker process XXXXX exited on signal 11" errors? Thank you in advance for your help.

We have been running NGINX 0.7.65 on freeBSD for a few months. Because of issues getting the fail-over to work properly, 1 week ago we migrated from freeBSD to Linux (Ubuntu) running version 0.7.65. In this first week, we saw perhaps 2 dozen "worker process XXXXX exited on signal 11" errors per hour and have been experiencing dropped web connections at a rate that seems to coincide with the "exited on signal 11" errors. We tried many different configuration changes, and finally this afternoon upgraded to 0.8.36. Unfortunately we continue to see the "worker process XXXXX exited on signal 11" errors.

Other possible factors: We have been using keepalived to verify that NGINX is accepting web traffic on port 80 every second.

This is our configuration file:
[code]
# Nginx configuration file
user nobody;
worker_processes 1;

events {
worker_connections 1024;
}

http {

gzip on;
gzip_types text/plain text/css application/x-javascript application/javascript;
gzip_disable "MSIE [1-6]\.";

# This controls upload size
client_max_body_size 45M;

# How long to wait for upstream server response (seconds)
proxy_read_timeout 600;

upstream php5 {
server 192.168.1.121 weight=1;
server 192.168.1.123 weight=1;
}


# keeps connection to same web servers
upstream webserversessions {
ip_hash;
server 192.168.1.121;
server 192.168.1.123;
}

## Default for all sites
server {
listen 80;
location / {
proxy_pass http://php5$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-By $server_name;
}

# Add expires headers
location ~* ^.+\.(js)$ {
expires modified +24h;
proxy_pass http://php5$request_uri;
}

# Stats reporting
location /nginx_status {
stub_status on;
access_log off;
allow 192.168.234.0/24;
allow 192.168.1.0/24;
deny all;
}
}

## maintain session required for openID
server {
listen 80;
server_name community.llli.org;
location / {
proxy_pass http://webserversessions$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}

## For site that needs sessions
server {
listen 80;
server_name files.golightly.com;
location / {
proxy_pass http://webserversessions$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-By $server_name;
}
}

## SSL sites ##

server { # Need to add this server section with unique IP for each SSL site we serve
listen 38.127.224.114:443;
ssl on;
ssl_certificate /etc/ssl/www.latchon.org.pem;
ssl_certificate_key /etc/ssl/private/www.latchon.org.key;
ssl_protocols SSLv2 SSLv3 TLSv1;
ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP;
ssl_prefer_server_ciphers on;

location / {
proxy_pass http://php5$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-By $server_name:443;
}
}

server {
listen 38.127.224.112:443;
ssl on;
ssl_certificate /etc/ssl/networking.cccu.org.pem;
ssl_certificate_key /etc/ssl/private/networking.cccu.org.key;
ssl_protocols SSLv2 SSLv3 TLSv1;
ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP;
ssl_prefer_server_ciphers on;

location / {
proxy_pass http://php5$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-By $server_name:443;
}
}

server {
listen 38.127.224.113:443;
ssl on;
ssl_certificate /etc/ssl/backstage.codenomicon.com.chain.pem;
ssl_certificate_key /etc/ssl/private/backstage.codenomicon.com.key;
ssl_protocols SSLv2 SSLv3 TLSv1;
ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP;
ssl_prefer_server_ciphers on;

location / {
proxy_pass http://php5$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-By $server_name:443;
}
}

}
[/code]