1 files changed, 74 insertions, 89 deletions

diff --git a/net/tipc/dbg.c b/net/tipc/dbg.c
index 834319e3b7e7..8ca9457250be 100644
--- a/net/tipc/dbg.c
+++ b/net/tipc/dbg.c
@@ -38,18 +38,44 @@
 #include "config.h"
 #include "dbg.h"
 
-static char print_string[TIPC_PB_MAX_STR];
-static DEFINE_SPINLOCK(print_lock);
+/*
+ * TIPC pre-defines the following print buffers:
+ *
+ * TIPC_NULL : null buffer (i.e. print nowhere)
+ * TIPC_CONS : system console
+ * TIPC_LOG  : TIPC log buffer
+ *
+ * Additional user-defined print buffers are also permitted.
+ */
 
-static struct print_buf null_buf = { NULL, 0, NULL, NULL };
+static struct print_buf null_buf = { NULL, 0, NULL, 0 };
 struct print_buf *TIPC_NULL = &null_buf;
 
-static struct print_buf cons_buf = { NULL, 0, NULL, NULL };
+static struct print_buf cons_buf = { NULL, 0, NULL, 1 };
 struct print_buf *TIPC_CONS = &cons_buf;
 
-static struct print_buf log_buf = { NULL, 0, NULL, NULL };
+static struct print_buf log_buf = { NULL, 0, NULL, 1 };
 struct print_buf *TIPC_LOG = &log_buf;
 
+/*
+ * Locking policy when using print buffers.
+ *
+ * 1) tipc_printf() uses 'print_lock' to protect against concurrent access to
+ * 'print_string' when writing to a print buffer. This also protects against
+ * concurrent writes to the print buffer being written to.
+ *
+ * 2) tipc_dump() and tipc_log_XXX() leverage the aforementioned
+ * use of 'print_lock' to protect against all types of concurrent operations
+ * on their associated print buffer (not just write operations).
+ *
+ * Note: All routines of the form tipc_printbuf_XXX() are lock-free, and rely
+ * on the caller to prevent simultaneous use of the print buffer(s) being
+ * manipulated.
+ */
+
+static char print_string[TIPC_PB_MAX_STR];
+static DEFINE_SPINLOCK(print_lock);
+
 
 #define FORMAT(PTR,LEN,FMT) \
 {\
@@ -60,27 +86,14 @@ struct print_buf *TIPC_LOG = &log_buf;
        *(PTR + LEN) = '\0';\
 }
 
-/*
- * Locking policy when using print buffers.
- *
- * The following routines use 'print_lock' for protection:
- * 1) tipc_printf()  - to protect its print buffer(s) and 'print_string'
- * 2) TIPC_TEE()     - to protect its print buffer(s)
- * 3) tipc_dump()    - to protect its print buffer(s) and 'print_string'
- * 4) tipc_log_XXX() - to protect TIPC_LOG
- *
- * All routines of the form tipc_printbuf_XXX() rely on the caller to prevent
- * simultaneous use of the print buffer(s) being manipulated.
- */
-
 /**
  * tipc_printbuf_init - initialize print buffer to empty
  * @pb: pointer to print buffer structure
  * @raw: pointer to character array used by print buffer
  * @size: size of character array
  *
- * Makes the print buffer a null device that discards anything written to it
- * if the character array is too small (or absent).
+ * Note: If the character array is too small (or absent), the print buffer
+ * becomes a null device that discards anything written to it.
  */
 
 void tipc_printbuf_init(struct print_buf *pb, char *raw, u32 size)
@@ -88,7 +101,7 @@ void tipc_printbuf_init(struct print_buf *pb, char *raw, u32 size)
 	pb->buf = raw;
 	pb->crs = raw;
 	pb->size = size;
-	pb->next = NULL;
+	pb->echo = 0;
 
 	if (size < TIPC_PB_MIN_SIZE) {
 		pb->buf = NULL;
@@ -105,7 +118,11 @@ void tipc_printbuf_init(struct print_buf *pb, char *raw, u32 size)
 
 void tipc_printbuf_reset(struct print_buf *pb)
 {
-	tipc_printbuf_init(pb, pb->buf, pb->size);
+	if (pb->buf != NULL) {
+		pb->crs = pb->buf;
+		pb->buf[0] = 0;
+		pb->buf[pb->size - 1] = ~0;
+	}
 }
 
 /**
@@ -182,7 +199,6 @@ void tipc_printbuf_move(struct print_buf *pb_to, struct print_buf *pb_from)
 		strcpy(pb_to->buf, "*** PRINT BUFFER MOVE ERROR ***");
 		pb_to->buf[pb_to->size - 1] = ~0;
 		pb_to->crs = strchr(pb_to->buf, 0);
-		pb_to->next = NULL;
 		return;
 	}
 
@@ -205,8 +221,8 @@ void tipc_printbuf_move(struct print_buf *pb_to, struct print_buf *pb_from)
 }
 
 /**
- * tipc_printf - append formatted output to print buffer chain
- * @pb: pointer to chain of print buffers (may be NULL)
+ * tipc_printf - append formatted output to print buffer
+ * @pb: pointer to print buffer
  * @fmt: formatted info to be printed
  */
 
@@ -215,66 +231,36 @@ void tipc_printf(struct print_buf *pb, const char *fmt, ...)
 	int chars_to_add;
 	int chars_left;
 	char save_char;
-	struct print_buf *pb_next;
 
 	spin_lock_bh(&print_lock);
+
 	FORMAT(print_string, chars_to_add, fmt);
 	if (chars_to_add >= TIPC_PB_MAX_STR)
 		strcpy(print_string, "*** PRINT BUFFER STRING TOO LONG ***");
 
-	while (pb) {
-		if (pb == TIPC_CONS)
-			printk(print_string);
-		else if (pb->buf) {
-			chars_left = pb->buf + pb->size - pb->crs - 1;
-			if (chars_to_add <= chars_left) {
-				strcpy(pb->crs, print_string);
-				pb->crs += chars_to_add;
-			} else if (chars_to_add >= (pb->size - 1)) {
-				strcpy(pb->buf, print_string + chars_to_add + 1
-				       - pb->size);
-				pb->crs = pb->buf + pb->size - 1;
-			} else {
-				strcpy(pb->buf, print_string + chars_left);
-				save_char = print_string[chars_left];
-				print_string[chars_left] = 0;
-				strcpy(pb->crs, print_string);
-				print_string[chars_left] = save_char;
-				pb->crs = pb->buf + chars_to_add - chars_left;
-			}
+	if (pb->buf) {
+		chars_left = pb->buf + pb->size - pb->crs - 1;
+		if (chars_to_add <= chars_left) {
+			strcpy(pb->crs, print_string);
+			pb->crs += chars_to_add;
+		} else if (chars_to_add >= (pb->size - 1)) {
+			strcpy(pb->buf, print_string + chars_to_add + 1
+			       - pb->size);
+			pb->crs = pb->buf + pb->size - 1;
+		} else {
+			strcpy(pb->buf, print_string + chars_left);
+			save_char = print_string[chars_left];
+			print_string[chars_left] = 0;
+			strcpy(pb->crs, print_string);
+			print_string[chars_left] = save_char;
+			pb->crs = pb->buf + chars_to_add - chars_left;
 		}
-		pb_next = pb->next;
-		pb->next = NULL;
-		pb = pb_next;
 	}
-	spin_unlock_bh(&print_lock);
-}
 
-/**
- * TIPC_TEE - perform next output operation on both print buffers
- * @b0: pointer to chain of print buffers (may be NULL)
- * @b1: pointer to print buffer to add to chain
- *
- * Returns pointer to print buffer chain.
- */
-
-struct print_buf *TIPC_TEE(struct print_buf *b0, struct print_buf *b1)
-{
-	struct print_buf *pb = b0;
+	if (pb->echo)
+		printk(print_string);
 
-	if (!b0 || (b0 == b1))
-		return b1;
-
-	spin_lock_bh(&print_lock);
-	while (pb->next) {
-		if ((pb->next == b1) || (pb->next == b0))
-			pb->next = pb->next->next;
-		else
-			pb = pb->next;
-	}
-	pb->next = b1;
 	spin_unlock_bh(&print_lock);
-	return b0;
 }
 
 /**
@@ -323,31 +309,28 @@ static void printbuf_dump(struct print_buf *pb)
 }
 
 /**
- * tipc_dump - dump non-console print buffer(s) to console
- * @pb: pointer to chain of print buffers
+ * tipc_dump - dump (non-console) print buffer to console
+ * @pb: pointer to print buffer
  */
 
 void tipc_dump(struct print_buf *pb, const char *fmt, ...)
 {
-	struct print_buf *pb_next;
 	int len;
 
+	if (pb == TIPC_CONS)
+		return;
+
 	spin_lock_bh(&print_lock);
+
 	FORMAT(print_string, len, fmt);
 	printk(print_string);
 
-	for (; pb; pb = pb->next) {
-		if (pb != TIPC_CONS) {
-			printk("\n---- Start of %s log dump ----\n\n",
-			       (pb == TIPC_LOG) ? "global" : "local");
-			printbuf_dump(pb);
-			tipc_printbuf_reset(pb);
-			printk("\n---- End of dump ----\n");
-		}
-		pb_next = pb->next;
-		pb->next = NULL;
-		pb = pb_next;
-	}
+	printk("\n---- Start of %s log dump ----\n\n",
+	       (pb == TIPC_LOG) ? "global" : "local");
+	printbuf_dump(pb);
+	tipc_printbuf_reset(pb);
+	printk("\n---- End of dump ----\n");
+
 	spin_unlock_bh(&print_lock);
 }
 
@@ -368,8 +351,10 @@ int tipc_log_resize(int log_size)
 	if (log_size) {
 		if (log_size < TIPC_PB_MIN_SIZE)
 			log_size = TIPC_PB_MIN_SIZE;
+		res = TIPC_LOG->echo;
 		tipc_printbuf_init(TIPC_LOG, kmalloc(log_size, GFP_ATOMIC),
 				   log_size);
+		TIPC_LOG->echo = res;
 		res = !TIPC_LOG->buf;
 	}
 	spin_unlock_bh(&print_lock);