sysvinit/showconsole-1.09-blogd-coarse-locking.diff

From: Olaf Kirch <okir@suse.de>
Subject: Use coarser locking for the log buffer

blogd claims and releases a mutex for every character it
writes into the log buffer. Change parselog to grab the lock
once, and release it when done parsing all of the input.

Signed-off-by: Olaf Kirch <okir@suse.de>

Index: showconsole-1.09/libconsole.c
===================================================================
--- showconsole-1.09/libconsole.c
+++ showconsole-1.09/libconsole.c   2009-01-26 16:58:00.000000000 +0100
@@ -346,9 +346,8 @@ static volatile ssize_t avail;
 
 static inline void resetlog(void) { tail = head = data; avail = 0; }
 
-static inline void storelog(const unsigned char *const buf, const size_t len)
+static inline void __storelog(const unsigned char *const buf, const size_t len)
 {
-    lock(&llock);
     if (len > end - tail) {
 	static int be_warned = 0;
 	if (!be_warned) {
@@ -360,13 +359,18 @@ static inline void storelog(const unsign
     memcpy(tail, buf, len);
     avail = (tail += len) - head;
 xout:
-    unlock(&llock);
     return;
 }
 
-static inline void addlog(const unsigned char c)
+static void storelog(const unsigned char *const buf, const size_t len)
 {
     lock(&llock);
+    __storelog(buf, len);
+    unlock(&llock);
+}
+
+static inline void __addlog(const unsigned char c)
+{
     if (end - tail <= 0) {
 	static int be_warned = 0;
 	if (!be_warned) {
@@ -378,10 +382,16 @@ static inline void addlog(const unsigned
     *tail = c;
     avail = (tail += 1) - head;
 xout:
-    unlock(&llock);
     return;
 }
 
+static void addlog(const unsigned char c)
+{
+    lock(&llock);
+    __addlog(c);
+    unlock(&llock);
+}
+
 static inline void writelog(void)
 {
     if (!flog)
@@ -492,6 +502,8 @@ static void parselog(unsigned char *buf,
     ssize_t r = s, up;
     unsigned char uprt[16];
 
+    lock(&llock);
+
     while (r > 0) {
 	c = (unsigned char)*buf;
 
@@ -506,25 +518,25 @@ static void parselog(unsigned char *buf,
 	    case 28 ... 31:
 		nl = 0;
 		spin = 0;
-		addlog('^'); addlog(c + 64);
+		__addlog('^'); __addlog(c + 64);
 		break;
 	    case '\n':
 		if (spin > 4)	/* last spinner line */
-		    storelog(prog, strlen((char*)prog));
+		    __storelog(prog, strlen((char*)prog));
 		nl = 1;
 		line++;
 		spin = 0;
-		addlog(c);
+		__addlog(c);
 		break;
 	    case '\r':
 		spin++;
 		if (spin < 5) {
 		    if (spin > 1)
-			addlog('\n');
+			__addlog('\n');
 		    nl = 1;
 		}
 		if (spin == 5)
-		    storelog((unsigned char*)"\n<progress bar skipped>\n", 24);
+		    __storelog((unsigned char*)"\n<progress bar skipped>\n", 24);
 		break;
 	    case 14:
 	    case 15:
@@ -543,8 +555,8 @@ static void parselog(unsigned char *buf,
 	    case 160 ... 255:
 		if (spin < 5) {
 		    if (spin == 1 && nl)
-			addlog('\n');
-		    addlog(c);
+			__addlog('\n');
+		    __addlog(c);
 		} else {		/* Seems to be a lengthy spinner line */
 		    static   int old = 0;
 		    static ssize_t p = 0;
@@ -561,14 +573,14 @@ static void parselog(unsigned char *buf,
 	    case 127:
 		nl = 0;
 		spin = 0;
-		addlog('^'); addlog('?');
+		__addlog('^'); __addlog('?');
 		break;
 	    case 128 ... 128+26:
 	    case 128+28 ... 159:
 		nl = 0;
 		spin = 0;
 		if ((up = snprintf((char*)uprt, sizeof(uprt), "\\%03o", c)) > 0)
-		    storelog(uprt, (size_t)up);
+		    __storelog(uprt, (size_t)up);
 		break;
 	    case 128+27:
 		spin = 0;
@@ -578,7 +590,7 @@ static void parselog(unsigned char *buf,
 		nl = 0;
 		spin = 0;
 		if ((up = snprintf((char*)uprt, sizeof(uprt), "0x%X", c)) > 0)
-		    storelog(uprt, (size_t)up);
+		    __storelog(uprt, (size_t)up);
 		break;
 	    }
 	    break;
@@ -597,11 +609,11 @@ static void parselog(unsigned char *buf,
 	    case 'E':
 	    case 'D':
 		if (spin > 4)	/* last spinner line */
-		    storelog(prog, strlen((char*)prog));
+		    __storelog(prog, strlen((char*)prog));
 		nl = 1;
 		line++;
 		spin = 0;
-		addlog('\n');
+		__addlog('\n');
 		break;
 	    case '(':
 		state = ESsetG0;
@@ -674,11 +686,14 @@ static void parselog(unsigned char *buf,
 		unsigned char echo[64];
 		ssize_t len;
 
+		/* Release the lock while doing IO */
+		unlock(&llock);
 		if ((len = snprintf(echo, sizeof(echo), "\033[%lu;%dR", line, nl)) > 0)
 		    safeout(fdread, echo, len);
 		else
 		    safeout(fdread, "\033R", 2);
 		tcdrain(fdread);
+		lock(&llock);
 	    }
 	    break;
 #endif
@@ -686,6 +701,8 @@ static void parselog(unsigned char *buf,
 	buf++;
 	r--;
     }
+
+    unlock(&llock);
 }
 
 static void copylog(const unsigned char *buf, const size_t s)