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Message-Id: 
 <3a4fe07e40e967622035844ff10ded1ed71d94fc.1640012469.git.gitgitgadget@gmail.com>
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Date: Mon, 20 Dec 2021 15:01:02 +0000
Subject: [PATCH 2/9] trace2: convert tr2tls_thread_ctx.thread_name from strbuf
 to char*
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To: git@vger.kernel.org
Cc: Jeff Hostetler <jeffhost@microsoft.com>,
        Jeff Hostetler <jeffhost@microsoft.com>
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From: Jeff Hostetler <jeffhost@microsoft.com>

From: Jeff Hostetler <jeffhost@microsoft.com>

Use a 'char *' to hold the thread name rather than a 'struct strbuf'.
The thread name is set when the thread is created and should not be
be modified afterwards.  Replace the strbuf with an allocated pointer
to make that more clear.

This was discussed in: https://lore.kernel.org/all/xmqqa6kdwo24.fsf@gitster.g/

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
 trace2/tr2_tgt_event.c |  2 +-
 trace2/tr2_tgt_perf.c  |  2 +-
 trace2/tr2_tls.c       | 16 +++++++++-------
 trace2/tr2_tls.h       |  2 +-
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/trace2/tr2_tgt_event.c b/trace2/tr2_tgt_event.c
index 3a0014417cc..ca48d00aebc 100644
--- a/trace2/tr2_tgt_event.c
+++ b/trace2/tr2_tgt_event.c
@@ -88,7 +88,7 @@ static void event_fmt_prepare(const char *event_name, const char *file,
 
 	jw_object_string(jw, "event", event_name);
 	jw_object_string(jw, "sid", tr2_sid_get());
-	jw_object_string(jw, "thread", ctx->thread_name.buf);
+	jw_object_string(jw, "thread", ctx->thread_name);
 
 	/*
 	 * In brief mode, only emit <time> on these 2 event types.
diff --git a/trace2/tr2_tgt_perf.c b/trace2/tr2_tgt_perf.c
index e4acca13d64..c3e57fcb3c0 100644
--- a/trace2/tr2_tgt_perf.c
+++ b/trace2/tr2_tgt_perf.c
@@ -106,7 +106,7 @@ static void perf_fmt_prepare(const char *event_name,
 
 	strbuf_addf(buf, "d%d | ", tr2_sid_depth());
 	strbuf_addf(buf, "%-*s | %-*s | ", TR2_MAX_THREAD_NAME,
-		    ctx->thread_name.buf, TR2FMT_PERF_MAX_EVENT_NAME,
+		    ctx->thread_name, TR2FMT_PERF_MAX_EVENT_NAME,
 		    event_name);
 
 	len = buf->len + TR2FMT_PERF_REPO_WIDTH;
diff --git a/trace2/tr2_tls.c b/trace2/tr2_tls.c
index 7da94aba522..cd8b9f2f0a0 100644
--- a/trace2/tr2_tls.c
+++ b/trace2/tr2_tls.c
@@ -35,6 +35,7 @@ struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name,
 					     uint64_t us_thread_start)
 {
 	struct tr2tls_thread_ctx *ctx = xcalloc(1, sizeof(*ctx));
+	struct strbuf buf_name = STRBUF_INIT;
 
 	/*
 	 * Implicitly "tr2tls_push_self()" to capture the thread's start
@@ -47,12 +48,13 @@ struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name,
 
 	ctx->thread_id = tr2tls_locked_increment(&tr2_next_thread_id);
 
-	strbuf_init(&ctx->thread_name, 0);
 	if (ctx->thread_id)
-		strbuf_addf(&ctx->thread_name, "th%02d:", ctx->thread_id);
-	strbuf_addstr(&ctx->thread_name, thread_name);
-	if (ctx->thread_name.len > TR2_MAX_THREAD_NAME)
-		strbuf_setlen(&ctx->thread_name, TR2_MAX_THREAD_NAME);
+		strbuf_addf(&buf_name, "th%02d:", ctx->thread_id);
+	strbuf_addstr(&buf_name, thread_name);
+	if (buf_name.len > TR2_MAX_THREAD_NAME)
+		strbuf_setlen(&buf_name, TR2_MAX_THREAD_NAME);
+
+	ctx->thread_name = strbuf_detach(&buf_name, NULL);
 
 	pthread_setspecific(tr2tls_key, ctx);
 
@@ -95,7 +97,7 @@ void tr2tls_unset_self(void)
 
 	pthread_setspecific(tr2tls_key, NULL);
 
-	strbuf_release(&ctx->thread_name);
+	free(ctx->thread_name);
 	free(ctx->array_us_start);
 	free(ctx);
 }
@@ -113,7 +115,7 @@ void tr2tls_pop_self(void)
 	struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
 
 	if (!ctx->nr_open_regions)
-		BUG("no open regions in thread '%s'", ctx->thread_name.buf);
+		BUG("no open regions in thread '%s'", ctx->thread_name);
 
 	ctx->nr_open_regions--;
 }
diff --git a/trace2/tr2_tls.h b/trace2/tr2_tls.h
index a90bd639d48..d968da6a679 100644
--- a/trace2/tr2_tls.h
+++ b/trace2/tr2_tls.h
@@ -9,7 +9,7 @@
 #define TR2_MAX_THREAD_NAME (24)
 
 struct tr2tls_thread_ctx {
-	struct strbuf thread_name;
+	char *thread_name;
 	uint64_t *array_us_start;
 	size_t alloc;
 	size_t nr_open_regions; /* plays role of "nr" in ALLOC_GROW */