I'm not officially working, but as my wife is not currently home, I
decided to sneak a peek at this patch ;-)
On Fri, 23 Nov 2018 13:41:40 +0000
Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx> wrote:
> This patch is a PoC about transforming libtraceevent
> 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.
>
> Signed-off-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
> ---
> tools/lib/traceevent/event-parse-local.h | 17 ++++++++++---
> tools/lib/traceevent/event-parse-thread.c | 29 +++++++++++++++++++++++
> tools/lib/traceevent/event-parse.c | 23 ++++++++++--------
> 3 files changed, 56 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..11f71ef8850b 100644
> --- a/tools/lib/traceevent/event-parse-local.h
> +++ b/tools/lib/traceevent/event-parse-local.h
> @@ -14,6 +14,17 @@ struct func_list;
> struct event_handler;
> struct func_resolver;
>
> +/* cache */
> +struct tep_thread_data {
> + struct tep_event *last_event;
We need to add a pointer to the tep handle itself. We don't want to use
the last event if it belonged to a different tep handle. Yes a thread
may have access to more than one tep handle at a time. Especially when
we start to do virt-server work.
> +};
> +
> +struct tep_thread_data_list {
> + pid_t tid;
> + struct tep_thread_data thr_data;
> + struct tep_thread_data_pool *next;
> +};
> +
I'm thinking that we should not add the "tep_" prefix for anything
that's not exposed outside the library. This can help us know what's
local and what's not. I know there's some things currently like that,
but perhaps we should change them too.
> struct tep_handle {
> int ref_count;
>
> @@ -83,9 +94,6 @@ struct tep_handle {
> struct event_handler *handlers;
> struct tep_function_handler *func_handlers;
>
> - /* cache */
> - struct tep_event *last_event;
> -
> char *trace_clock;
> };
>
> @@ -96,4 +104,7 @@ 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();
> +void tep_destroy_thread_local();
> +
> #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..775d953041ab
> --- /dev/null
> +++ b/tools/lib/traceevent/event-parse-thread.c
> @@ -0,0 +1,29 @@
> +// 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 __maybe_unused)
> +{
> + if (tep_thread_local)
> + return tep_thread_local;
> +
> + tep_thread_local = calloc(1, sizeof(struct tep_thread_data));
> + return tep_thread_local;
> +}
> +
> +
> +void tep_destroy_thread_local()
> +{
> + free(tep_thread_local);
> + tep_thread_local = NULL;
> +}
> +
> 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);
> /* 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)
&& local->tep == pevent &&
(but we should also rename pevent to tep, but that's another patch
series ;-)
> + 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;
> + if (local)
{
> + local->last_event = *eventptr;
local->tep = pevent;
}
> 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);
> struct tep_event *event = NULL;
> int i;
>
> - 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;
Same here.
-- Steve
> return event;
> }
>
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