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From: "Jeff Hostetler via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Jeff Hostetler" <git@jeffhostetler.com>,
	"Derrick Stolee" <stolee@gmail.com>,
	"Matheus Tavares" <matheus.bernardino@usp.br>,
	"Johannes Sixt" <j6t@kdbg.org>,
	"Jeff Hostetler" <jeffhost@microsoft.com>,
	"Jeff Hostetler" <jeffhost@microsoft.com>
Subject: [PATCH v2 3/9] trace2: defer free of thread local storage until program exit.
Date: Tue, 28 Dec 2021 19:36:36 +0000	[thread overview]
Message-ID: <11c8d8cdf1a9c0e4f840a295c7401014404e119d.1640720202.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1099.v2.git.1640720202.gitgitgadget@gmail.com>

From: Jeff Hostetler <jeffhost@microsoft.com>

Defer freeing of the Trace2 per-thread thread local storage until
program exit.  Create a global list to own them.

Trace2 thread local storage data is allocated when a thread is created
and associated with that thread.  Previously, that storage was deleted
when the thread exited.  Now at thread exit, we simply disassociate
the data from the thread and let the global list manage the cleanup.

This will be used by a later commit when we add "counters" and
stopwatch-style "timers" to the Trace2 API.  We will add those fields
to the thread local storage block and allow each thread to efficiently
(without locks) accumulate counter and timer data.  At program exit,
the main thread will run thru the global list and compute and report
totals before freeing the list.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
 trace2/tr2_tls.c | 38 +++++++++++++++++++++++++++++++-------
 trace2/tr2_tls.h |  3 ++-
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/trace2/tr2_tls.c b/trace2/tr2_tls.c
index ed99a234b95..78538d5e522 100644
--- a/trace2/tr2_tls.c
+++ b/trace2/tr2_tls.c
@@ -15,6 +15,18 @@ static uint64_t tr2tls_us_start_process;
 static pthread_mutex_t tr2tls_mutex;
 static pthread_key_t tr2tls_key;
 
+/*
+ * This list owns all of the thread-specific CTX data.
+ *
+ * While a thread is alive it is associated with a CTX (owned by this
+ * list) and that CTX is installed in the thread's TLS data area.
+ * When a thread exits, it is disassociated from its CTX, but the (now
+ * dormant) CTX is held in this list until program exit.
+ *
+ * Similarly, `tr2tls_thread_main` points to a CTX contained within
+ * this list.
+ */
+static struct tr2tls_thread_ctx *tr2tls_ctx_list; /* modify under lock */
 static int tr2_next_thread_id; /* modify under lock */
 
 void tr2tls_start_process_clock(void)
@@ -56,6 +68,14 @@ struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name,
 	ctx->array_us_start = (uint64_t *)xcalloc(ctx->alloc, sizeof(uint64_t));
 	ctx->array_us_start[ctx->nr_open_regions++] = us_thread_start;
 
+	/*
+	 * Link this CTX into the CTX list and make it the head.
+	 */
+	pthread_mutex_lock(&tr2tls_mutex);
+	ctx->next_ctx = tr2tls_ctx_list;
+	tr2tls_ctx_list = ctx;
+	pthread_mutex_unlock(&tr2tls_mutex);
+
 	pthread_setspecific(tr2tls_key, ctx);
 
 	return ctx;
@@ -91,14 +111,7 @@ int tr2tls_is_main_thread(void)
 
 void tr2tls_unset_self(void)
 {
-	struct tr2tls_thread_ctx *ctx;
-
-	ctx = tr2tls_get_self();
-
 	pthread_setspecific(tr2tls_key, NULL);
-
-	free(ctx->array_us_start);
-	free(ctx);
 }
 
 void tr2tls_push_self(uint64_t us_now)
@@ -162,11 +175,22 @@ void tr2tls_init(void)
 
 void tr2tls_release(void)
 {
+	struct tr2tls_thread_ctx *ctx = tr2tls_ctx_list;
+
 	tr2tls_unset_self();
 	tr2tls_thread_main = NULL;
 
 	pthread_mutex_destroy(&tr2tls_mutex);
 	pthread_key_delete(tr2tls_key);
+
+	while (ctx) {
+		struct tr2tls_thread_ctx *next = ctx->next_ctx;
+
+		free(ctx->array_us_start);
+		free(ctx);
+
+		ctx = next;
+	}
 }
 
 int tr2tls_locked_increment(int *p)
diff --git a/trace2/tr2_tls.h b/trace2/tr2_tls.h
index 64d97c5ac03..889010ec1ff 100644
--- a/trace2/tr2_tls.h
+++ b/trace2/tr2_tls.h
@@ -4,6 +4,7 @@
 #include "strbuf.h"
 
 struct tr2tls_thread_ctx {
+	struct tr2tls_thread_ctx *next_ctx;
 	uint64_t *array_us_start;
 	size_t alloc;
 	size_t nr_open_regions; /* plays role of "nr" in ALLOC_GROW */
@@ -37,7 +38,7 @@ struct tr2tls_thread_ctx *tr2tls_get_self(void);
 int tr2tls_is_main_thread(void);
 
 /*
- * Free our TLS data.
+ * Disassociate thread's TLS CTX data from the thread.
  */
 void tr2tls_unset_self(void);
 
-- 
gitgitgadget


  parent reply	other threads:[~2021-12-28 19:36 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-20 15:01 [PATCH 0/9] Trace2 stopwatch timers and global counters Jeff Hostetler via GitGitGadget
2021-12-20 15:01 ` [PATCH 1/9] trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx Jeff Hostetler via GitGitGadget
2021-12-20 15:01 ` [PATCH 2/9] trace2: convert tr2tls_thread_ctx.thread_name from strbuf to char* Jeff Hostetler via GitGitGadget
2021-12-20 16:31   ` Ævar Arnfjörð Bjarmason
2021-12-20 19:07     ` Jeff Hostetler
2021-12-20 19:35       ` Ævar Arnfjörð Bjarmason
2021-12-22 16:32         ` Jeff Hostetler
2021-12-21  7:33     ` Junio C Hamano
2021-12-21  7:22   ` Junio C Hamano
2021-12-22 16:28     ` Jeff Hostetler
2021-12-22 19:57       ` Junio C Hamano
2021-12-20 15:01 ` [PATCH 3/9] trace2: defer free of TLS CTX until program exit Jeff Hostetler via GitGitGadget
2021-12-21  7:30   ` Junio C Hamano
2021-12-22 21:59     ` Jeff Hostetler
2021-12-22 22:56       ` Junio C Hamano
2021-12-22 23:04         ` Jeff Hostetler
2021-12-23  7:38         ` Johannes Sixt
2021-12-23 18:18           ` Junio C Hamano
2021-12-27 18:51             ` Jeff Hostetler
2021-12-20 15:01 ` [PATCH 4/9] trace2: add thread-name override to event target Jeff Hostetler via GitGitGadget
2021-12-20 15:01 ` [PATCH 5/9] trace2: add thread-name override to perf target Jeff Hostetler via GitGitGadget
2021-12-20 15:01 ` [PATCH 6/9] trace2: add timer events to perf and event target formats Jeff Hostetler via GitGitGadget
2021-12-20 16:39   ` Ævar Arnfjörð Bjarmason
2021-12-20 19:44     ` Jeff Hostetler
2021-12-21 14:20   ` Derrick Stolee
2021-12-20 15:01 ` [PATCH 7/9] trace2: add stopwatch timers Jeff Hostetler via GitGitGadget
2021-12-20 16:42   ` Ævar Arnfjörð Bjarmason
2021-12-22 21:38     ` Jeff Hostetler
2021-12-21 14:45   ` Derrick Stolee
2021-12-22 21:57     ` Jeff Hostetler
2021-12-20 15:01 ` [PATCH 8/9] trace2: add counter events to perf and event target formats Jeff Hostetler via GitGitGadget
2021-12-20 16:51   ` Ævar Arnfjörð Bjarmason
2021-12-22 22:56     ` Jeff Hostetler
2021-12-20 15:01 ` [PATCH 9/9] trace2: add global counters Jeff Hostetler via GitGitGadget
2021-12-20 17:14   ` Ævar Arnfjörð Bjarmason
2021-12-22 22:18     ` Jeff Hostetler
2021-12-21 14:51 ` [PATCH 0/9] Trace2 stopwatch timers and " Derrick Stolee
2021-12-21 23:27   ` Matheus Tavares
2021-12-28 19:36 ` [PATCH v2 " Jeff Hostetler via GitGitGadget
2021-12-28 19:36   ` [PATCH v2 1/9] trace2: use size_t alloc,nr_open_regions in tr2tls_thread_ctx Jeff Hostetler via GitGitGadget
2021-12-29  0:48     ` Ævar Arnfjörð Bjarmason
2021-12-28 19:36   ` [PATCH v2 2/9] trace2: convert tr2tls_thread_ctx.thread_name from strbuf to flex array Jeff Hostetler via GitGitGadget
2021-12-29  1:11     ` Ævar Arnfjörð Bjarmason
2021-12-29 16:46       ` Jeff Hostetler
2021-12-28 19:36   ` Jeff Hostetler via GitGitGadget [this message]
2021-12-28 19:36   ` [PATCH v2 4/9] trace2: add thread-name override to event target Jeff Hostetler via GitGitGadget
2021-12-28 19:36   ` [PATCH v2 5/9] trace2: add thread-name override to perf target Jeff Hostetler via GitGitGadget
2021-12-29  1:48     ` Ævar Arnfjörð Bjarmason
2021-12-29 17:15       ` Jeff Hostetler
2021-12-28 19:36   ` [PATCH v2 6/9] trace2: add timer events to perf and event target formats Jeff Hostetler via GitGitGadget
2021-12-28 19:36   ` [PATCH v2 7/9] trace2: add stopwatch timers Jeff Hostetler via GitGitGadget
2021-12-28 19:36   ` [PATCH v2 8/9] trace2: add counter events to perf and event target formats Jeff Hostetler via GitGitGadget
2021-12-28 19:36   ` [PATCH v2 9/9] trace2: add global counters Jeff Hostetler via GitGitGadget
2021-12-29  1:54   ` [PATCH v2 0/9] Trace2 stopwatch timers and " Ævar Arnfjörð Bjarmason
2021-12-30 16:42     ` Jeff Hostetler

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