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changeset 3293:8abb88374c6c

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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.
author Igor Sysoev <igor@sysoev.ru>
date Wed, 04 Nov 2009 19:41:08 +0000
parents 6ed04ab2d062
children 04cfc09b8b8d
files src/os/unix/ngx_process_cycle.c
diffstat 1 files changed, 12 insertions(+), 2 deletions(-) [+]
line wrap: on
line diff
--- 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 {