diff --git a/defs.h b/defs.h
index ca1ac79..98650e8 100644
--- a/defs.h
+++ b/defs.h
@@ -2239,6 +2239,7 @@ struct offset_table {                    /* stash of commonly-used offsets */
 	long mnt_namespace_mounts;
 	long mnt_namespace_nr_mounts;
 	long mount_mnt_node;
+	long log_caller_id;
 };
 
 struct size_table {         /* stash of commonly-used sizes */
@@ -6108,12 +6109,13 @@ void dump_log(int);
 void parse_kernel_version(char *);
 
 #define LOG_LEVEL(v) ((v) & 0x07)
-#define SHOW_LOG_LEVEL (0x1)
-#define SHOW_LOG_DICT  (0x2)
-#define SHOW_LOG_TEXT  (0x4)
-#define SHOW_LOG_AUDIT (0x8)
-#define SHOW_LOG_CTIME (0x10)
-#define SHOW_LOG_SAFE  (0x20)
+#define SHOW_LOG_LEVEL    (0x1)
+#define SHOW_LOG_DICT     (0x2)
+#define SHOW_LOG_TEXT     (0x4)
+#define SHOW_LOG_AUDIT    (0x8)
+#define SHOW_LOG_CTIME   (0x10)
+#define SHOW_LOG_SAFE    (0x20)
+#define SHOW_LOG_CALLER  (0x40)
 void set_cpu(int);
 void clear_machdep_cache(void);
 struct stack_hook *gather_text_list(struct bt_info *);
@@ -7588,6 +7590,10 @@ int calc_kaslr_offset(ulong *, ulong *);
  */
 void dump_lockless_record_log(int);
 
+/* caller_id default and max character sizes based on pid field size */
+#define PID_CHARS_MAX 16        /* Max Number of PID characters */
+#define PID_CHARS_DEFAULT 8     /* Default number of PID characters */
+
 /*
  *  gnu_binutils.c
  */
diff --git a/help.c b/help.c
index 623b09c..a9c4d30 100644
--- a/help.c
+++ b/help.c
@@ -4024,7 +4024,7 @@ NULL
 char *help_log[] = {
 "log",
 "dump system message buffer",
-"[-Ttdmas]",
+"[-Ttdmasc]",
 "  This command dumps the kernel log_buf contents in chronological order.  The",
 "  command supports the older log_buf formats, which may or may not contain a",
 "  timestamp inserted prior to each message, as well as the newer variable-length", 
@@ -4047,7 +4047,11 @@ char *help_log[] = {
 "        been copied out to the user-space audit daemon.",
 "    -s  Dump the printk logs remaining in kernel safe per-CPU buffers that",
 "        have not been flushed out to log_buf.",
-" ",        
+"    -c  Display the caller id field that identifies either the thread id or",
+"        the CPU id (if in CPU context) that called printk(), if available.",
+"        Generally available on Linux 5.1 to 5.9 kernels configured with",
+"        CONFIG_PRINTK_CALLER or Linux 5.10 and later kernels.",
+" ",
 "\nEXAMPLES",
 "  Dump the kernel message buffer:\n",
 "    %s> log",
@@ -4215,6 +4219,17 @@ char *help_log[] = {
 "    CPU: 0  ADDR: ffff8ca4fbc1ad00 LEN: 0  MESSAGE_LOST: 0",
 "      (empty)",
 "    ...",
+" ",
+"  Display the caller id that identifies the thread id of the task (begins",
+"  with 'T') or the processor id (begins with 'C' for in CPU context) that",
+"  called printk(), if available.\n",
+"    %s> log -c",
+"    ...",
+"    [    0.014179] [     T1] Secure boot disabled",
+"    [    0.014179] [    T29] RAMDISK: [mem 0x3cf4f000-0x437bbfff]",
+"    [    0.198789] [     C0] DMAR: DRHD: handling fault status reg 3",
+"    ...",
+
 NULL               
 };
 
diff --git a/kernel.c b/kernel.c
index 6dcf414..1728b70 100644
--- a/kernel.c
+++ b/kernel.c
@@ -5089,7 +5089,7 @@ cmd_log(void)
 
 	msg_flags = 0;
 
-        while ((c = getopt(argcnt, args, "Ttdmas")) != EOF) {
+        while ((c = getopt(argcnt, args, "Ttdmasc")) != EOF) {
                 switch(c)
                 {
 		case 'T':
@@ -5110,6 +5110,9 @@ cmd_log(void)
 		case 's':
 			msg_flags |= SHOW_LOG_SAFE;
 			break;
+		case 'c':
+			msg_flags |= SHOW_LOG_CALLER;
+			break;
                 default:
                         argerrs++;
                         break;
@@ -5369,6 +5372,25 @@ dump_log_entry(char *logptr, int msg_flags)
 		fprintf(fp, "%s", buf);
 	}
 
+	/*
+	 * The PRINTK_CALLER id field was introduced with Linux-5.1 so if
+	 * requested, Kernel version >= 5.1 and field exists print caller_id.
+	 */
+	if (msg_flags & SHOW_LOG_CALLER &&
+			VALID_MEMBER(log_caller_id)) {
+		const unsigned int cpuid = 0x80000000;
+		char cbuf[PID_CHARS_MAX];
+		unsigned int cid;
+
+		/* Get id type, isolate just id value in cid for print */
+		cid = UINT(logptr + OFFSET(log_caller_id));
+		sprintf(cbuf, "%c%d", (cid & cpuid) ? 'C' : 'T', cid & ~cpuid);
+		sprintf(buf, "[%*s] ", PID_CHARS_DEFAULT, cbuf);
+
+		ilen += strlen(buf);
+		fprintf(fp, "%s", buf);
+	}
+
 	level = LOG_LEVEL(level);
 
 	if (msg_flags & SHOW_LOG_LEVEL) {
@@ -5424,6 +5446,7 @@ dump_variable_length_record_log(int msg_flags)
 			 * from log to printk_log.  See 62e32ac3505a0cab.
 			 */
 			log_struct_name = "printk_log";
+			MEMBER_OFFSET_INIT(log_caller_id, "printk_log", "caller_id");
 		} else 
 			log_struct_name = "log";
 
diff --git a/printk.c b/printk.c
index 8658016..be842a7 100644
--- a/printk.c
+++ b/printk.c
@@ -9,6 +9,7 @@ struct prb_map {
 	unsigned long desc_ring_count;
 	char *descs;
 	char *infos;
+	unsigned int pid_max_chars;
 
 	char *text_data_ring;
 	unsigned long text_data_ring_size;
@@ -162,6 +163,24 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
 		fprintf(fp, "%s", buf);
 	}
 
+	/*
+	 * The lockless ringbuffer introduced in Linux-5.10 always has
+	 * the caller_id field available, so if requested, print it.
+	 */
+	if (msg_flags & SHOW_LOG_CALLER) {
+		const unsigned int cpuid = 0x80000000;
+		char cbuf[PID_CHARS_MAX];
+		unsigned int cid;
+
+		/* Get id type, isolate id value in cid for print */
+		cid = UINT(info + OFFSET(printk_info_caller_id));
+		sprintf(cbuf, "%c%d", (cid & cpuid) ? 'C' : 'T', cid & ~cpuid);
+		sprintf(buf, "[%*s] ", m->pid_max_chars, cbuf);
+
+		ilen += strlen(buf);
+		fprintf(fp, "%s", buf);
+	}
+
 	if (msg_flags & SHOW_LOG_LEVEL) {
 		level = UCHAR(info + OFFSET(printk_info_level)) >> 5;
 		sprintf(buf, "<%x>", level);
@@ -262,6 +281,21 @@ dump_lockless_record_log(int msg_flags)
 		goto out_text_data;
 	}
 
+	/* If caller_id was requested, get the pid_max value for print */
+	if (msg_flags & SHOW_LOG_CALLER) {
+		unsigned int pidmax;
+
+		get_symbol_data("pid_max", sizeof(pidmax), &pidmax);
+		if (pidmax <= 99999)
+			m.pid_max_chars = 6;
+		else if (pidmax <= 999999)
+			m.pid_max_chars = 7;
+		else
+			m.pid_max_chars = PID_CHARS_DEFAULT;
+	} else {
+		m.pid_max_chars = PID_CHARS_DEFAULT;
+	}
+
 	/* ready to go */
 
 	tail_id = ULONG(m.desc_ring + OFFSET(prb_desc_ring_tail_id) +
diff --git a/symbols.c b/symbols.c
index b07b101..cbc9ed1 100644
--- a/symbols.c
+++ b/symbols.c
@@ -11550,6 +11550,7 @@ dump_offset_table(char *spec, ulong makestruct)
 		OFFSET(log_level));
 	fprintf(fp, "               log_flags_level: %ld\n",
 		OFFSET(log_flags_level));
+	fprintf(fp, "                 log_caller_id: %ld\n", OFFSET(log_caller_id));
 
 	fprintf(fp, "               printk_info_seq: %ld\n", OFFSET(printk_info_seq));
 	fprintf(fp, "           printk_info_ts_nseq: %ld\n", OFFSET(printk_info_ts_nsec));