On Mon, 26 Nov 2018 13:22:59 +0000
Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx> wrote:
> This patch is a PoC about transforming libtraceevent
FYI, when posting a proof of concept, you can add it to the subject:
[POC][PATCH v2] tools/lib/traceevent: make libtraceevent thread safe
This lets people know that it's not something to be applied.
> into a thread safe library. It implements per thread local
> storage and internal APIs to access it. It covers only
> tep->last_event cache, but easily can be extended with all
> library's thread sensitive data.
>
> [v2 - added local thread data per tep context]
>
> Signed-off-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
> ---
> tools/lib/traceevent/event-parse-local.h | 14 ++++--
> tools/lib/traceevent/event-parse-thread.c | 57 +++++++++++++++++++++++
> tools/lib/traceevent/event-parse.c | 23 +++++----
> 3 files changed, 81 insertions(+), 13 deletions(-)
> create mode 100644 tools/lib/traceevent/event-parse-thread.c
>
> diff --git a/tools/lib/traceevent/event-parse-local.h b/tools/lib/traceevent/event-parse-local.h
> index 9a092dd4a86d..6fa0f05b29c3 100644
> --- a/tools/lib/traceevent/event-parse-local.h
> +++ b/tools/lib/traceevent/event-parse-local.h
> @@ -14,6 +14,14 @@ struct func_list;
> struct event_handler;
> struct func_resolver;
>
> +/* cache */
> +struct tep_thread_data {
> + struct tep_handle *tep;
> + struct tep_thread_data *next;
> +
> + struct tep_event *last_event;
> +};
> +
> struct tep_handle {
> int ref_count;
>
> @@ -83,9 +91,6 @@ struct tep_handle {
> struct event_handler *handlers;
> struct tep_function_handler *func_handlers;
>
> - /* cache */
> - struct tep_event *last_event;
> -
> char *trace_clock;
> };
>
> @@ -96,4 +101,7 @@ unsigned short tep_data2host2(struct tep_handle *pevent, unsigned short data);
> unsigned int tep_data2host4(struct tep_handle *pevent, unsigned int data);
> unsigned long long tep_data2host8(struct tep_handle *pevent, unsigned long long data);
>
> +struct tep_thread_data *tep_get_thread_local(struct tep_handle *tep);
> +void tep_destroy_thread_local(struct tep_handle *tep);
> +
> #endif /* _PARSE_EVENTS_INT_H */
> diff --git a/tools/lib/traceevent/event-parse-thread.c b/tools/lib/traceevent/event-parse-thread.c
> new file mode 100644
> index 000000000000..39350dc82c5d
> --- /dev/null
> +++ b/tools/lib/traceevent/event-parse-thread.c
> @@ -0,0 +1,57 @@
> +// SPDX-License-Identifier: LGPL-2.1
> +/*
> + * Copyright (C) 2009, 2010 Red Hat Inc, Steven Rostedt <srostedt@xxxxxxxxxx>
> + *
> + */
> +
> +#include "event-parse.h"
> +#include "event-parse-local.h"
> +#include "event-utils.h"
> +
> +static __thread struct tep_thread_data *tep_thread_local;
> +
> +
> +struct tep_thread_data *tep_get_thread_local(struct tep_handle *tep)
> +{
> + struct tep_thread_data *local = tep_thread_local;
> +
> + while(local) {
I wouldn't do make it a list. I would either cache the last one, and if
the tep doesn't match, then return NULL (not a match).
> + if (local->tep == tep)
> + return local;
> + local = local->next;
> + }
> +
> + local = calloc(1, sizeof(struct tep_thread_data));
Let's create a new function to create it:
tep_alloc_thread_local(tep, event);
> + if(local) {
> + local->tep = tep;
> + local->next = tep_thread_local;
> + tep_thread_local = local;
> + }
> + return local;
> +}
> +
> +
> +void tep_destroy_thread_local(struct tep_handle *tep)
> +{
> + struct tep_thread_data **local, *del;
> +
> + if(!tep_thread_local)
> + return;
> + local = &tep_thread_local;
> +
> + while(*local) {
> + if ((*local)->tep == tep) {
> + tep_thread_local = (*local)->next;
> + free(*local);
> + return;
> + }
> + if ((*local)->next && (*local)->next->tep == tep) {
> + del = (*local)->next;
> + (*local)->next = (*local)->next->next;
> + free(del);
> + return;
> + }
> + local = &((*local)->next);
> + }
> +}
> +
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index a5048c1b9bec..25f4ceab9a58 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -3485,10 +3485,11 @@ struct tep_event *tep_find_event(struct tep_handle *pevent, int id)
> struct tep_event **eventptr;
> struct tep_event key;
> struct tep_event *pkey = &key;
> -
> + struct tep_thread_data *local = tep_get_thread_local(pevent);
Let's make this:
local = tep_get_thread_local(pevent, id);
if (local)
return local->last_event;
> /* Check cache first */
> - if (pevent->last_event && pevent->last_event->id == id)
> - return pevent->last_event;
> +
> + if (local && local->last_event && local->last_event->id == id)
> + return local->last_event;
>
> key.id = id;
>
> @@ -3496,7 +3497,8 @@ struct tep_event *tep_find_event(struct tep_handle *pevent, int id)
> sizeof(*pevent->events), events_id_cmp);
>
> if (eventptr) {
> - pevent->last_event = *eventptr;
tep_alloc_thread_local(tep, *eventptr);
And have that function do the assignment if it got allocated.
> + if (local)
> + local->last_event = *eventptr;
> return *eventptr;
> }
>
> @@ -3516,13 +3518,14 @@ struct tep_event *
> tep_find_event_by_name(struct tep_handle *pevent,
> const char *sys, const char *name)
> {
> + struct tep_thread_data *local = tep_get_thread_local(pevent);
Make it: local = tep_get_thread_local_name(pevent, name);
> struct tep_event *event = NULL;
> int i;
>
if (local)
return local->last_event;
-- Steve
> - if (pevent->last_event &&
> - strcmp(pevent->last_event->name, name) == 0 &&
> - (!sys || strcmp(pevent->last_event->system, sys) == 0))
> - return pevent->last_event;
> + if (local && local->last_event &&
> + strcmp(local->last_event->name, name) == 0 &&
> + (!sys || strcmp(local->last_event->system, sys) == 0))
> + return local->last_event;
>
> for (i = 0; i < pevent->nr_events; i++) {
> event = pevent->events[i];
> @@ -3535,8 +3538,8 @@ tep_find_event_by_name(struct tep_handle *pevent,
> }
> if (i == pevent->nr_events)
> event = NULL;
> -
> - pevent->last_event = event;
> + if (local)
> + local->last_event = event;
> return event;
> }
>
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