Patch from Fillod Stephane:

  You will find in the attached file "syslog.patch" a patch which adds
  config options to set at compile time the size of the circular buffer,
  and some documentation update.


git-svn-id: svn://busybox.net/trunk/busybox@8129 69ca8d6d-28ef-0310-b511-8ec308f3f277

5 files changed, 70 insertions, 12 deletions

diff --git a/docs/busybox.sgml b/docs/busybox.sgml
index 1d2e9268a..ac400c7c8 100644
--- a/docs/busybox.sgml
+++ b/docs/busybox.sgml
@@ -1976,6 +1976,38 @@
                 </para>
         </sect1>
 
+        <sect1 id="logread">
+            <title>logread</title>
+
+                <para>
+                Usage: logread [OPTION]...
+                </para>
+
+                <para>
+                Shows the messages from syslogd (using circular buffer).
+                </para>
+
+                <para>
+                Options:
+                </para>
+
+                <para>
+                <screen>
+                        -f      Output data as the log grows.
+                </screen>
+                </para>
+
+                <para>
+                Example:
+                </para>
+
+                <para>
+                <screen>
+                        $ logread
+                </screen>
+                </para>
+        </sect1>
+
         <sect1 id="ls">
             <title>ls</title>
 
@@ -3110,7 +3142,7 @@
                         -O FILE Use an alternate log file (default=/var/log/messages)
                         -R HOST[:PORT] Log remotely to IP or hostname on PORT (default PORT=514/UDP)
                         -L      Log locally as well as network logging (default is network only)
-                        -C      Log to a circular buffer. Read this buffer using 'logread'
+                        -C [size(KiB)] Log to a circular buffer. Read this buffer using 'logread'
                 </screen>
                 </para>
 
diff --git a/include/usage.h b/include/usage.h
index 6db0385fb..ea1b5d5fe 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -1458,10 +1458,12 @@
         "root\n" 
 
 #define logread_trivial_usage \
-        ""
+        "[OPTION]..."
 
 #define logread_full_usage \
-        "Shows the messages from syslogd (using circular buffer)."
+        "Shows the messages from syslogd (using circular buffer).\n\n"
+        "Options:\n" \
+        "\t-f\t\toutput data as the log grows"
 
 #define losetup_trivial_usage \
         "[OPTION]... LOOPDEVICE FILE\n" \
@@ -2280,7 +2282,7 @@
         "\n\t-R HOST[:PORT]\tLog to IP or hostname on PORT (default PORT=514/UDP)\n" \
         "\t-L\t\tLog locally and via network logging (default is network only)") \
         USAGE_IPC_LOG( \
-        "\n\t-C\t\tLog to a circular buffer (read the buffer using logread)")
+        "\n\t-C [size(KiB)]\tLog to a circular buffer (read the buffer using logread)")
 #define syslogd_example_usage \
         "$ syslogd -R masterlog:514\n" \
         "$ syslogd -R 192.168.1.1:601\n"
diff --git a/sysklogd/Config.in b/sysklogd/Config.in
index cb2ee0865..a671f59f1 100644
--- a/sysklogd/Config.in
+++ b/sysklogd/Config.in
@@ -56,6 +56,14 @@ config CONFIG_FEATURE_IPC_SYSLOG
           entire filesystem, which may cause your system to
           break badly.
 
+config CONFIG_FEATURE_IPC_SYSLOG_BUFFER_SIZE
+        int "    Circular buffer size in Kbytes (minimum 4KB)"
+        default 16
+        depends on CONFIG_FEATURE_IPC_SYSLOG
+        help
+          This option sets the size of the circular buffer
+          used to record system log messages.
+
 config CONFIG_LOGREAD
         bool "  logread"
         default y
@@ -66,6 +74,17 @@ config CONFIG_LOGREAD
           utility will allow you to read the messages that are
           stored in the syslogd circular buffer.
 
+config CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
+        bool "    logread double buffering"
+        default n
+        depends on CONFIG_LOGREAD
+        help
+          'logread' ouput to slow serial terminals can have 
+          side effects on syslog because of the semaphore.
+          This option make logread to double buffer copy 
+          from circular buffer, minimizing semaphore 
+          contention at some minor memory expense.
+
 config CONFIG_KLOGD
         bool "klogd"
         default n
diff --git a/sysklogd/logread.c b/sysklogd/logread.c
index 524178fe8..207e78b57 100644
--- a/sysklogd/logread.c
+++ b/sysklogd/logread.c
@@ -108,8 +108,7 @@ extern int logread_main(int argc, char **argv)
         i = follow ? buf->tail : buf->head;
 
         do {
-#undef RC_LOGREAD
-#ifdef RC_LOGREAD
+#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
                 char *buf_data;
                 int log_len,j;
 #endif
@@ -128,7 +127,7 @@ extern int logread_main(int argc, char **argv)
                 }
         
                 // Read Memory 
-#ifdef RC_LOGREAD
+#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
                 log_len = buf->tail - i;
                 if (log_len < 0)
                         log_len += buf->size;
@@ -155,7 +154,7 @@ extern int logread_main(int argc, char **argv)
                 // release the lock on the log chain
                 sem_up(log_semid);
 
-#ifdef RC_LOGREAD
+#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
                 for (j=0; j < log_len; j+=strlen(buf_data+j)+1) {
                         printf("%s", buf_data+j);
                         if (follow)
diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index 622500e48..42426ed80 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -94,6 +94,12 @@ static int local_logging = FALSE;
 
 /* circular buffer variables/structures */
 #ifdef CONFIG_FEATURE_IPC_SYSLOG
+
+#if CONFIG_FEATURE_IPC_SYSLOG_BUFFER_SIZE < 4
+#error Sorry, you must set the syslogd buffer size to at least 4KB.
+#error Please check CONFIG_FEATURE_IPC_SYSLOG_BUFFER_SIZE
+#endif
+
 #include <sys/ipc.h>
 #include <sys/sem.h>
 #include <sys/shm.h>
@@ -114,7 +120,7 @@ static struct sembuf SMwdn[3] = { {0, 0}, {1, 0}, {1, +1} };	// set SMwdn
 
 static int shmid = -1;  // ipc shared memory id
 static int s_semid = -1;        // ipc semaphore id
-static int data_size = 16000;   // default data size
+static int shm_size = ((CONFIG_FEATURE_IPC_SYSLOG_BUFFER_SIZE)*1024);   // default shm size
 static int circular_logging = FALSE;
 
 /*
@@ -156,7 +162,7 @@ void ipcsyslog_cleanup(void)
 void ipcsyslog_init(void)
 {
         if (buf == NULL) {
-                if ((shmid = shmget(KEY_ID, data_size, IPC_CREAT | 1023)) == -1) {
+                if ((shmid = shmget(KEY_ID, shm_size, IPC_CREAT | 1023)) == -1) {
                         bb_perror_msg_and_die("shmget");
                 }
 
@@ -164,7 +170,7 @@ void ipcsyslog_init(void)
                         bb_perror_msg_and_die("shmat");
                 }
 
-                buf->size = data_size - sizeof(*buf);
+                buf->size = shm_size - sizeof(*buf);
                 buf->head = buf->tail = 0;
 
                 // we'll trust the OS to set initial semval to 0 (let's hope)
@@ -654,7 +660,7 @@ extern int syslogd_main(int argc, char **argv)
                         if (optarg) {
                                 int buf_size = atoi(optarg);
                                 if (buf_size >= 4) {
-                                        data_size = buf_size;
+                                        shm_size = buf_size;
                                 }
                         }
                         circular_logging = TRUE;