tracing: Add support for named hist triggers

Allow users to define 'named' hist triggers. All triggers created
with the same 'name=xxx' option will update the same shared histogram
data.

This expands the hist trigger syntax from this:

# echo hist:keys=xxx ... [ if filter] > event/trigger

to this:

# echo hist:name=xxx:keys=xxx ... [ if filter] > event/trigger

Named histograms must use a 'compatible' set of keys and values, which
means each event added to a set of named triggers must have the same
names and types.

Reading the 'hist' file of any of the participating events will
produce the same output as any other participating event, which is to
be expected since they share the same data.

Link: http://lkml.kernel.org/r/1db[e-mail]

Signed-off-by: Tom Zanussi <[e-mail]>
Tested-by: Masami Hiramatsu <[e-mail]>
Reviewed-by: Namhyung Kim <[e-mail]>
Signed-off-by: Steven Rostedt <[e-mail]>

Documentation/trace/events.txt

···
 
         hist:keys=<field1[,field2,...]>[:values=<field1[,field2,...]>]
           [:sort=<field1[,field2,...]>][:size=#entries][:pause][:continue]
-          [:clear] [if <filter>]
+          [:clear][:name=histname1] [if <filter>]
 
   When a matching event is hit, an entry is added to a hash table
   using the key(s) and value(s) named.  Keys and values correspond to
···
   specified by the 'sort' keyword.  If more than one field is
   specified, the result will be a 'sort within a sort': the first key
   is taken to be the primary sort key and the second the secondary
-  key.
+  key.  If a hist trigger is given a name using the 'name' parameter,
+  its histogram data will be shared with other triggers of the same
+  name, and trigger hits will update this common data.  Only triggers
+  with 'compatible' fields can be combined in this way; triggers are
+  'compatible' if the fields named in the trigger share the same
+  number and type of fields and those fields also have the same names.
+  Note that any two events always share the compatible 'hitcount' and
+  'stacktrace' fields and can therefore be combined using those
+  fields, however pointless that may be.
 
   'hist' triggers add a 'hist' file to each event's subdirectory.
   Reading the 'hist' file for the event will dump the hash table in
   its entirety to stdout.  If there are multiple hist triggers
   attached to an event, there will be a table for each trigger in the
-  output.  Each printed hash table entry is a simple list of the keys
-  and values comprising the entry; keys are printed first and are
-  delineated by curly braces, and are followed by the set of value
-  fields for the entry.  By default, numeric fields are displayed as
-  base-10 integers.  This can be modified by appending any of the
-  following modifiers to the field name:
+  output.  The table displayed for a named trigger will be the same as
+  any other instance having the same name. Each printed hash table
+  entry is a simple list of the keys and values comprising the entry;
+  keys are printed first and are delineated by curly braces, and are
+  followed by the set of value fields for the entry.  By default,
+  numeric fields are displayed as base-10 integers.  This can be
+  modified by appending any of the following modifiers to the field
+  name:
 
         .hex        display a number as a hex value
 	.sym        display an address as a symbol
···
     Totals:
         Hits: 0
         Entries: 0
+        Dropped: 0
+
+  Named triggers can be used to have triggers share a common set of
+  histogram data.  This capability is mostly useful for combining the
+  output of events generated by tracepoints contained inside inline
+  functions, but names can be used in a hist trigger on any event.
+  For example, these two triggers when hit will update the same 'len'
+  field in the shared 'foo' histogram data:
+
+    # echo 'hist:name=foo:keys=skbaddr.hex:vals=len' > \
+           /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
+    # echo 'hist:name=foo:keys=skbaddr.hex:vals=len' > \
+           /sys/kernel/debug/tracing/events/net/netif_rx/trigger
+
+  You can see that they're updating common histogram data by reading
+  each event's hist files at the same time:
+
+    # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist;
+      cat /sys/kernel/debug/tracing/events/net/netif_rx/hist
+
+    # event histogram
+    #
+    # trigger info: hist:name=foo:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active]
+    #
+
+    { skbaddr: ffff88000ad53500 } hitcount:          1  len:         46
+    { skbaddr: ffff8800af5a1500 } hitcount:          1  len:         76
+    { skbaddr: ffff8800d62a1900 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bccb00 } hitcount:          1  len:        468
+    { skbaddr: ffff8800d3c69900 } hitcount:          1  len:         46
+    { skbaddr: ffff88009ff09100 } hitcount:          1  len:         52
+    { skbaddr: ffff88010f13ab00 } hitcount:          1  len:        168
+    { skbaddr: ffff88006a54f400 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bcc500 } hitcount:          1  len:        260
+    { skbaddr: ffff880064505000 } hitcount:          1  len:         46
+    { skbaddr: ffff8800baf24e00 } hitcount:          1  len:         32
+    { skbaddr: ffff88009fe0ad00 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d3edff00 } hitcount:          1  len:         44
+    { skbaddr: ffff88009fe0b400 } hitcount:          1  len:        168
+    { skbaddr: ffff8800a1c55a00 } hitcount:          1  len:         40
+    { skbaddr: ffff8800d2bcd100 } hitcount:          1  len:         40
+    { skbaddr: ffff880064505f00 } hitcount:          1  len:        174
+    { skbaddr: ffff8800a8bff200 } hitcount:          1  len:        160
+    { skbaddr: ffff880044e3cc00 } hitcount:          1  len:         76
+    { skbaddr: ffff8800a8bfe700 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bcdc00 } hitcount:          1  len:         32
+    { skbaddr: ffff8800a1f64800 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bcde00 } hitcount:          1  len:        988
+    { skbaddr: ffff88006a5dea00 } hitcount:          1  len:         46
+    { skbaddr: ffff88002e37a200 } hitcount:          1  len:         44
+    { skbaddr: ffff8800a1f32c00 } hitcount:          2  len:        676
+    { skbaddr: ffff88000ad52600 } hitcount:          2  len:        107
+    { skbaddr: ffff8800a1f91e00 } hitcount:          2  len:         92
+    { skbaddr: ffff8800af5a0200 } hitcount:          2  len:        142
+    { skbaddr: ffff8800d2bcc600 } hitcount:          2  len:        220
+    { skbaddr: ffff8800ba36f500 } hitcount:          2  len:         92
+    { skbaddr: ffff8800d021f800 } hitcount:          2  len:         92
+    { skbaddr: ffff8800a1f33600 } hitcount:          2  len:        675
+    { skbaddr: ffff8800a8bfff00 } hitcount:          3  len:        138
+    { skbaddr: ffff8800d62a1300 } hitcount:          3  len:        138
+    { skbaddr: ffff88002e37a100 } hitcount:          4  len:        184
+    { skbaddr: ffff880064504400 } hitcount:          4  len:        184
+    { skbaddr: ffff8800a8bfec00 } hitcount:          4  len:        184
+    { skbaddr: ffff88000ad53700 } hitcount:          5  len:        230
+    { skbaddr: ffff8800d2bcdb00 } hitcount:          5  len:        196
+    { skbaddr: ffff8800a1f90000 } hitcount:          6  len:        276
+    { skbaddr: ffff88006a54f900 } hitcount:          6  len:        276
+
+    Totals:
+        Hits: 81
+        Entries: 42
+        Dropped: 0
+    # event histogram
+    #
+    # trigger info: hist:name=foo:keys=skbaddr.hex:vals=hitcount,len:sort=hitcount:size=2048 [active]
+    #
+
+    { skbaddr: ffff88000ad53500 } hitcount:          1  len:         46
+    { skbaddr: ffff8800af5a1500 } hitcount:          1  len:         76
+    { skbaddr: ffff8800d62a1900 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bccb00 } hitcount:          1  len:        468
+    { skbaddr: ffff8800d3c69900 } hitcount:          1  len:         46
+    { skbaddr: ffff88009ff09100 } hitcount:          1  len:         52
+    { skbaddr: ffff88010f13ab00 } hitcount:          1  len:        168
+    { skbaddr: ffff88006a54f400 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bcc500 } hitcount:          1  len:        260
+    { skbaddr: ffff880064505000 } hitcount:          1  len:         46
+    { skbaddr: ffff8800baf24e00 } hitcount:          1  len:         32
+    { skbaddr: ffff88009fe0ad00 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d3edff00 } hitcount:          1  len:         44
+    { skbaddr: ffff88009fe0b400 } hitcount:          1  len:        168
+    { skbaddr: ffff8800a1c55a00 } hitcount:          1  len:         40
+    { skbaddr: ffff8800d2bcd100 } hitcount:          1  len:         40
+    { skbaddr: ffff880064505f00 } hitcount:          1  len:        174
+    { skbaddr: ffff8800a8bff200 } hitcount:          1  len:        160
+    { skbaddr: ffff880044e3cc00 } hitcount:          1  len:         76
+    { skbaddr: ffff8800a8bfe700 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bcdc00 } hitcount:          1  len:         32
+    { skbaddr: ffff8800a1f64800 } hitcount:          1  len:         46
+    { skbaddr: ffff8800d2bcde00 } hitcount:          1  len:        988
+    { skbaddr: ffff88006a5dea00 } hitcount:          1  len:         46
+    { skbaddr: ffff88002e37a200 } hitcount:          1  len:         44
+    { skbaddr: ffff8800a1f32c00 } hitcount:          2  len:        676
+    { skbaddr: ffff88000ad52600 } hitcount:          2  len:        107
+    { skbaddr: ffff8800a1f91e00 } hitcount:          2  len:         92
+    { skbaddr: ffff8800af5a0200 } hitcount:          2  len:        142
+    { skbaddr: ffff8800d2bcc600 } hitcount:          2  len:        220
+    { skbaddr: ffff8800ba36f500 } hitcount:          2  len:         92
+    { skbaddr: ffff8800d021f800 } hitcount:          2  len:         92
+    { skbaddr: ffff8800a1f33600 } hitcount:          2  len:        675
+    { skbaddr: ffff8800a8bfff00 } hitcount:          3  len:        138
+    { skbaddr: ffff8800d62a1300 } hitcount:          3  len:        138
+    { skbaddr: ffff88002e37a100 } hitcount:          4  len:        184
+    { skbaddr: ffff880064504400 } hitcount:          4  len:        184
+    { skbaddr: ffff8800a8bfec00 } hitcount:          4  len:        184
+    { skbaddr: ffff88000ad53700 } hitcount:          5  len:        230
+    { skbaddr: ffff8800d2bcdb00 } hitcount:          5  len:        196
+    { skbaddr: ffff8800a1f90000 } hitcount:          6  len:        276
+    { skbaddr: ffff88006a54f900 } hitcount:          6  len:        276
+
+    Totals:
+        Hits: 81
+        Entries: 42
+        Dropped: 0
+
+  And here's an example that shows how to combine histogram data from
+  any two events even if they don't share any 'compatible' fields
+  other than 'hitcount' and 'stacktrace'.  These commands create a
+  couple of triggers named 'bar' using those fields:
+
+    # echo 'hist:name=bar:key=stacktrace:val=hitcount' > \
+           /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
+    # echo 'hist:name=bar:key=stacktrace:val=hitcount' > \
+          /sys/kernel/debug/tracing/events/net/netif_rx/trigger
+
+  And displaying the output of either shows some interesting if
+  somewhat confusing output:
+
+    # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
+    # cat /sys/kernel/debug/tracing/events/net/netif_rx/hist
+
+    # event histogram
+    #
+    # trigger info: hist:name=bar:keys=stacktrace:vals=hitcount:sort=hitcount:size=2048 [active]
+    #
+
+    { stacktrace:
+             _do_fork+0x18e/0x330
+             kernel_thread+0x29/0x30
+             kthreadd+0x154/0x1b0
+             ret_from_fork+0x3f/0x70
+    } hitcount:          1
+    { stacktrace:
+             netif_rx_internal+0xb2/0xd0
+             netif_rx_ni+0x20/0x70
+             dev_loopback_xmit+0xaa/0xd0
+             ip_mc_output+0x126/0x240
+             ip_local_out_sk+0x31/0x40
+             igmp_send_report+0x1e9/0x230
+             igmp_timer_expire+0xe9/0x120
+             call_timer_fn+0x39/0xf0
+             run_timer_softirq+0x1e1/0x290
+             __do_softirq+0xfd/0x290
+             irq_exit+0x98/0xb0
+             smp_apic_timer_interrupt+0x4a/0x60
+             apic_timer_interrupt+0x6d/0x80
+             cpuidle_enter+0x17/0x20
+             call_cpuidle+0x3b/0x60
+             cpu_startup_entry+0x22d/0x310
+    } hitcount:          1
+    { stacktrace:
+             netif_rx_internal+0xb2/0xd0
+             netif_rx_ni+0x20/0x70
+             dev_loopback_xmit+0xaa/0xd0
+             ip_mc_output+0x17f/0x240
+             ip_local_out_sk+0x31/0x40
+             ip_send_skb+0x1a/0x50
+             udp_send_skb+0x13e/0x270
+             udp_sendmsg+0x2bf/0x980
+             inet_sendmsg+0x67/0xa0
+             sock_sendmsg+0x38/0x50
+             SYSC_sendto+0xef/0x170
+             SyS_sendto+0xe/0x10
+             entry_SYSCALL_64_fastpath+0x12/0x6a
+    } hitcount:          2
+    { stacktrace:
+             netif_rx_internal+0xb2/0xd0
+             netif_rx+0x1c/0x60
+             loopback_xmit+0x6c/0xb0
+             dev_hard_start_xmit+0x219/0x3a0
+             __dev_queue_xmit+0x415/0x4f0
+             dev_queue_xmit_sk+0x13/0x20
+             ip_finish_output2+0x237/0x340
+             ip_finish_output+0x113/0x1d0
+             ip_output+0x66/0xc0
+             ip_local_out_sk+0x31/0x40
+             ip_send_skb+0x1a/0x50
+             udp_send_skb+0x16d/0x270
+             udp_sendmsg+0x2bf/0x980
+             inet_sendmsg+0x67/0xa0
+             sock_sendmsg+0x38/0x50
+             ___sys_sendmsg+0x14e/0x270
+    } hitcount:         76
+    { stacktrace:
+             netif_rx_internal+0xb2/0xd0
+             netif_rx+0x1c/0x60
+             loopback_xmit+0x6c/0xb0
+             dev_hard_start_xmit+0x219/0x3a0
+             __dev_queue_xmit+0x415/0x4f0
+             dev_queue_xmit_sk+0x13/0x20
+             ip_finish_output2+0x237/0x340
+             ip_finish_output+0x113/0x1d0
+             ip_output+0x66/0xc0
+             ip_local_out_sk+0x31/0x40
+             ip_send_skb+0x1a/0x50
+             udp_send_skb+0x16d/0x270
+             udp_sendmsg+0x2bf/0x980
+             inet_sendmsg+0x67/0xa0
+             sock_sendmsg+0x38/0x50
+             ___sys_sendmsg+0x269/0x270
+    } hitcount:         77
+    { stacktrace:
+             netif_rx_internal+0xb2/0xd0
+             netif_rx+0x1c/0x60
+             loopback_xmit+0x6c/0xb0
+             dev_hard_start_xmit+0x219/0x3a0
+             __dev_queue_xmit+0x415/0x4f0
+             dev_queue_xmit_sk+0x13/0x20
+             ip_finish_output2+0x237/0x340
+             ip_finish_output+0x113/0x1d0
+             ip_output+0x66/0xc0
+             ip_local_out_sk+0x31/0x40
+             ip_send_skb+0x1a/0x50
+             udp_send_skb+0x16d/0x270
+             udp_sendmsg+0x2bf/0x980
+             inet_sendmsg+0x67/0xa0
+             sock_sendmsg+0x38/0x50
+             SYSC_sendto+0xef/0x170
+    } hitcount:         88
+    { stacktrace:
+             _do_fork+0x18e/0x330
+             SyS_clone+0x19/0x20
+             entry_SYSCALL_64_fastpath+0x12/0x6a
+    } hitcount:        244
+
+    Totals:
+        Hits: 489
+        Entries: 7
         Dropped: 0

kernel/trace/trace.c

···
 	"\t            [:sort=<field1[,field2,...]>]\n"
 	"\t            [:size=#entries]\n"
 	"\t            [:pause][:continue][:clear]\n"
+	"\t            [:name=histname1]\n"
 	"\t            [if <filter>]\n\n"
 	"\t    When a matching event is hit, an entry is added to a hash\n"
 	"\t    table using the key(s) and value(s) named, and the value of a\n"
···
 	"\t    specified using the 'sort' keyword.  The sort direction can\n"
 	"\t    be modified by appending '.descending' or '.ascending' to a\n"
 	"\t    sort field.  The 'size' parameter can be used to specify more\n"
-	"\t    or fewer than the default 2048 entries for the hashtable size.\n\n"
+	"\t    or fewer than the default 2048 entries for the hashtable size.\n"
+	"\t    If a hist trigger is given a name using the 'name' parameter,\n"
+	"\t    its histogram data will be shared with other triggers of the\n"
+	"\t    same name, and trigger hits will update this common data.\n\n"
 	"\t    Reading the 'hist' file for the event will dump the hash\n"
 	"\t    table in its entirety to stdout.  If there are multiple hist\n"
 	"\t    triggers attached to an event, there will be a table for each\n"
-	"\t    trigger in the output.  The default format used to display a\n"
-	"\t    given field can be modified by appending any of the following\n"
-	"\t    modifiers to the field name, as applicable:\n\n"
+	"\t    trigger in the output.  The table displayed for a named\n"
+	"\t    trigger will be the same as any other instance having the\n"
+	"\t    same name.  The default format used to display a given field\n"
+	"\t    can be modified by appending any of the following modifiers\n"
+	"\t    to the field name, as applicable:\n\n"
 	"\t            .hex        display a number as a hex value\n"
 	"\t            .sym        display an address as a symbol\n"
 	"\t            .sym-offset display an address as a symbol and offset\n"

kernel/trace/trace_events_hist.c

···
 	char		*keys_str;
 	char		*vals_str;
 	char		*sort_key_str;
+	char		*name;
 	bool		pause;
 	bool		cont;
 	bool		clear;
···
 	if (!attrs)
 		return;
 
+	kfree(attrs->name);
 	kfree(attrs->sort_key_str);
 	kfree(attrs->keys_str);
 	kfree(attrs->vals_str);
···
 			attrs->vals_str = kstrdup(str, GFP_KERNEL);
 		else if (strncmp(str, "sort=", strlen("sort=")) == 0)
 			attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
+		else if (strncmp(str, "name=", strlen("name=")) == 0)
+			attrs->name = kstrdup(str, GFP_KERNEL);
 		else if (strcmp(str, "pause") == 0)
 			attrs->pause = true;
 		else if ((strcmp(str, "cont") == 0) ||
···
 	struct hist_field *key_field;
 	unsigned int i;
 
-	seq_puts(m, "hist:keys=");
+	seq_puts(m, "hist:");
+
+	if (data->name)
+		seq_printf(m, "%s:", data->name);
+
+	seq_puts(m, "keys=");
 
 	for_each_hist_key_field(i, hist_data) {
 		key_field = hist_data->fields[i];
···
 	return 0;
 }
 
+static int event_hist_trigger_init(struct event_trigger_ops *ops,
+				   struct event_trigger_data *data)
+{
+	struct hist_trigger_data *hist_data = data->private_data;
+
+	if (!data->ref && hist_data->attrs->name)
+		save_named_trigger(hist_data->attrs->name, data);
+
+	data->ref++;
+
+	return 0;
+}
+
 static void event_hist_trigger_free(struct event_trigger_ops *ops,
 				    struct event_trigger_data *data)
 {
···
 
 	data->ref--;
 	if (!data->ref) {
+		if (data->name)
+			del_named_trigger(data);
 		trigger_data_free(data);
 		destroy_hist_data(hist_data);
 	}
···
 static struct event_trigger_ops event_hist_trigger_ops = {
 	.func			= event_hist_trigger,
 	.print			= event_hist_trigger_print,
-	.init			= event_trigger_init,
+	.init			= event_hist_trigger_init,
 	.free			= event_hist_trigger_free,
+};
+
+static int event_hist_trigger_named_init(struct event_trigger_ops *ops,
+					 struct event_trigger_data *data)
+{
+	data->ref++;
+
+	save_named_trigger(data->named_data->name, data);
+
+	event_hist_trigger_init(ops, data->named_data);
+
+	return 0;
+}
+
+static void event_hist_trigger_named_free(struct event_trigger_ops *ops,
+					  struct event_trigger_data *data)
+{
+	if (WARN_ON_ONCE(data->ref <= 0))
+		return;
+
+	event_hist_trigger_free(ops, data->named_data);
+
+	data->ref--;
+	if (!data->ref) {
+		del_named_trigger(data);
+		trigger_data_free(data);
+	}
+}
+
+static struct event_trigger_ops event_hist_trigger_named_ops = {
+	.func			= event_hist_trigger,
+	.print			= event_hist_trigger_print,
+	.init			= event_hist_trigger_named_init,
+	.free			= event_hist_trigger_named_free,
 };
 
 static struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
···
 static void hist_clear(struct event_trigger_data *data)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
-	bool paused;
 
-	paused = data->paused;
-	data->paused = true;
+	if (data->name)
+		pause_named_trigger(data);
 
 	synchronize_sched();
 
 	tracing_map_clear(hist_data->map);
 
-	data->paused = paused;
+	if (data->name)
+		unpause_named_trigger(data);
+}
+
+static bool compatible_field(struct ftrace_event_field *field,
+			     struct ftrace_event_field *test_field)
+{
+	if (field == test_field)
+		return true;
+	if (field == NULL || test_field == NULL)
+		return false;
+	if (strcmp(field->name, test_field->name) != 0)
+		return false;
+	if (strcmp(field->type, test_field->type) != 0)
+		return false;
+	if (field->size != test_field->size)
+		return false;
+	if (field->is_signed != test_field->is_signed)
+		return false;
+
+	return true;
 }
 
 static bool hist_trigger_match(struct event_trigger_data *data,
-			       struct event_trigger_data *data_test)
+			       struct event_trigger_data *data_test,
+			       struct event_trigger_data *named_data,
+			       bool ignore_filter)
 {
 	struct tracing_map_sort_key *sort_key, *sort_key_test;
 	struct hist_trigger_data *hist_data, *hist_data_test;
 	struct hist_field *key_field, *key_field_test;
 	unsigned int i;
+
+	if (named_data && (named_data != data_test) &&
+	    (named_data != data_test->named_data))
+		return false;
+
+	if (!named_data && is_named_trigger(data_test))
+		return false;
 
 	hist_data = data->private_data;
 	hist_data_test = data_test->private_data;
···
 	    hist_data->n_sort_keys != hist_data_test->n_sort_keys)
 		return false;
 
-	if ((data->filter_str && !data_test->filter_str) ||
-	    (!data->filter_str && data_test->filter_str))
-		return false;
+	if (!ignore_filter) {
+		if ((data->filter_str && !data_test->filter_str) ||
+		   (!data->filter_str && data_test->filter_str))
+			return false;
+	}
 
 	for_each_hist_field(i, hist_data) {
 		key_field = hist_data->fields[i];
···
 
 		if (key_field->flags != key_field_test->flags)
 			return false;
-		if (key_field->field != key_field_test->field)
+		if (!compatible_field(key_field->field, key_field_test->field))
 			return false;
 		if (key_field->offset != key_field_test->offset)
 			return false;
···
 			return false;
 	}
 
-	if (data->filter_str &&
+	if (!ignore_filter && data->filter_str &&
 	    (strcmp(data->filter_str, data_test->filter_str) != 0))
 		return false;
 
···
 				 struct trace_event_file *file)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
-	struct event_trigger_data *test;
+	struct event_trigger_data *test, *named_data = NULL;
 	int ret = 0;
+
+	if (hist_data->attrs->name) {
+		named_data = find_named_trigger(hist_data->attrs->name);
+		if (named_data) {
+			if (!hist_trigger_match(data, named_data, named_data,
+						true)) {
+				ret = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+	if (hist_data->attrs->name && !named_data)
+		goto new;
 
 	list_for_each_entry_rcu(test, &file->triggers, list) {
 		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
-			if (!hist_trigger_match(data, test))
+			if (!hist_trigger_match(data, test, named_data, false))
 				continue;
 			if (hist_data->attrs->pause)
 				test->paused = true;
···
 			goto out;
 		}
 	}
-
+ new:
 	if (hist_data->attrs->cont || hist_data->attrs->clear) {
 		ret = -ENOENT;
 		goto out;
+	}
+
+	if (named_data) {
+		destroy_hist_data(data->private_data);
+		data->private_data = named_data->private_data;
+		set_named_trigger_data(data, named_data);
+		data->ops = &event_hist_trigger_named_ops;
 	}
 
 	if (hist_data->attrs->pause)
···
 	ret++;
 
 	update_cond_flag(file);
+
 	if (trace_event_trigger_enable_disable(file, 1) < 0) {
 		list_del_rcu(&data->list);
 		update_cond_flag(file);
···
 				    struct event_trigger_data *data,
 				    struct trace_event_file *file)
 {
-	struct event_trigger_data *test;
+	struct hist_trigger_data *hist_data = data->private_data;
+	struct event_trigger_data *test, *named_data = NULL;
 	bool unregistered = false;
+
+	if (hist_data->attrs->name)
+		named_data = find_named_trigger(hist_data->attrs->name);
 
 	list_for_each_entry_rcu(test, &file->triggers, list) {
 		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
-			if (!hist_trigger_match(data, test))
+			if (!hist_trigger_match(data, test, named_data, false))
 				continue;
 			unregistered = true;
 			list_del_rcu(&test->list);