# HG changeset patch
# User Igor Sysoev <igor@sysoev.ru>
# Date 1257363668 0
# Node ID 8abb88374c6cac1b0efe7ddc626fd17a0fcd3145
# Parent  6ed04ab2d06233f6d73be1ead9369c206a1cbda1
Fix a bug introduced in r2032: After a child process has read a terminate
message from a channel, the process tries to read the channel again.
The kernel (at least FreeBSD) may preempt the process and sends a SIGIO
signal to a master process. The master process sends a new terminate message,
the kernel switches again to the the child process, and the child process
reads the messages instead of an EAGAIN error. And this may repeat over
and over. Being that the child process can not exit the cycle and test
the termination flag set by the message handler.

The fix disallow the master process to send a new terminate message on
SIGIO signal reception. It may send the message only on SIGALARM signal.

diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -86,7 +86,7 @@ ngx_master_process_cycle(ngx_cycle_t *cy
     u_char            *p;
     size_t             size;
     ngx_int_t          i;
-    ngx_uint_t         n;
+    ngx_uint_t         n, sigio;
     sigset_t           set;
     struct itimerval   itv;
     ngx_uint_t         live;
@@ -139,11 +139,13 @@ ngx_master_process_cycle(ngx_cycle_t *cy
 
     ngx_new_binary = 0;
     delay = 0;
+    sigio = 0;
     live = 1;
 
     for ( ;; ) {
         if (delay) {
             if (ngx_sigalrm) {
+                sigio = 0;
                 delay *= 2;
                 ngx_sigalrm = 0;
             }
@@ -168,7 +170,8 @@ ngx_master_process_cycle(ngx_cycle_t *cy
 
         ngx_time_update(0, 0);
 
-        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "wake up");
+        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
+                       "wake up, sigio %i", sigio);
 
         if (ngx_reap) {
             ngx_reap = 0;
@@ -186,6 +189,13 @@ ngx_master_process_cycle(ngx_cycle_t *cy
                 delay = 50;
             }
 
+            if (sigio) {
+                sigio--;
+                continue;
+            }
+
+            sigio = ccf->worker_processes + 2 /* cache processes */;
+
             if (delay > 1000) {
                 ngx_signal_worker_processes(cycle, SIGKILL);
             } else {