3 files changed, 80 insertions, 94 deletions

diff --git a/net/tipc/core.h b/net/tipc/core.h
index 325404fd4eb5..7042ef377262 100644
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -66,7 +66,6 @@
 
 struct tipc_msg;
 extern struct print_buf *TIPC_NULL, *TIPC_CONS, *TIPC_LOG;
-extern struct print_buf *TIPC_TEE(struct print_buf *, struct print_buf *);
 void tipc_msg_print(struct print_buf*,struct tipc_msg *,const char*);
 void tipc_printf(struct print_buf *, const char *fmt, ...);
 void tipc_dump(struct print_buf*,const char *fmt, ...);
@@ -98,11 +97,13 @@ void tipc_dump(struct print_buf*,const char *fmt, ...);
  * TIPC_CONS               : system console
  * TIPC_LOG                : TIPC log buffer
  * &buf                    : user-defined buffer (struct print_buf *)
- * TIPC_TEE(&buf_a,&buf_b) : list of buffers (eg. TIPC_TEE(TIPC_CONS,TIPC_LOG))
+ *
+ * Note: TIPC_LOG is configured to echo its output to the system console;
+ *       user-defined buffers can be configured to do the same thing.
  */
 
 #ifndef TIPC_OUTPUT
-#define TIPC_OUTPUT TIPC_TEE(TIPC_CONS,TIPC_LOG)
+#define TIPC_OUTPUT TIPC_LOG
 #endif
 
 #ifndef DBG_OUTPUT
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);
diff --git a/net/tipc/dbg.h b/net/tipc/dbg.h
index 6b00062bf040..5ef1bc8f64ef 100644
--- a/net/tipc/dbg.h
+++ b/net/tipc/dbg.h
@@ -42,14 +42,14 @@
  * @buf: pointer to character array containing print buffer contents
  * @size: size of character array
  * @crs: pointer to first unused space in character array (i.e. final NUL)
- * @next: used to link print buffers when printing to more than one at a time
+ * @echo: echo output to system console if non-zero
  */
 
 struct print_buf {
         char *buf;
         u32 size;
         char *crs;
-        struct print_buf *next;
+        int echo;
 };
 
 #define TIPC_PB_MIN_SIZE 64     /* minimum size for a print buffer's array */