transport-helper: fix TSAN race in transfer_debug()
Currently, transfer_debug() lazily initializes a static variable based on GIT_TRANSLOOP_DEBUG. Since the function may be called from multiple worker threads, this initialization is racy and is therefore suppressed in .tsan-suppressions. Initialize the variable in bidirectional_transfer_loop() before any worker threads or processes are created. This patch removes the race and allows dropping the corresponding TSAN suppression. Signed-off-by: Pushkar Singh <pushkarkumarsingh1970@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Pushkar Singh committed
Jun 9, 2026 at 13:47 UTC
85704eda1820b350a9916b17d6d25fa33f68207d
2 files changed
+8
-12
.tsan-suppressions
-1
index 5ba86d6845..d84883bd90 100644
--- a/.tsan-suppressions
+++ b/.tsan-suppressions
@@ -7,7 +7,6 @@
# A static variable is written to racily, but we always write the same value, so
# in practice it (hopefully!) doesn't matter.
race:^want_color$
-race:^transfer_debug$
# A boolean value, which tells whether the replace_map has been initialized or
# not, is read racily with an update. As this variable is written to only once,
transport-helper.c
+8
-11
index 4614036c99..8eee2de14b 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -1343,24 +1343,18 @@ int transport_helper_init(struct transport *transport, const char *name)
/* This should be enough to hold debugging message. */
#define PBUFFERSIZE 8192
+static int transfer_debug_enabled = -1;
+
/* Print bidirectional transfer loop debug message. */
__attribute__((format (printf, 1, 2)))
static void transfer_debug(const char *fmt, ...)
{
- /*
- * NEEDSWORK: This function is sometimes used from multiple threads, and
- * we end up using debug_enabled racily. That "should not matter" since
- * we always write the same value, but it's still wrong. This function
- * is listed in .tsan-suppressions for the time being.
- */
-
va_list args;
char msgbuf[PBUFFERSIZE];
- static int debug_enabled = -1;
- if (debug_enabled < 0)
- debug_enabled = getenv("GIT_TRANSLOOP_DEBUG") ? 1 : 0;
- if (!debug_enabled)
+ if (transfer_debug_enabled < 0)
+ BUG("somebody forgot to check GIT_TRANSLOOP_DEBUG!");
+ if (!transfer_debug_enabled)
return;
va_start(args, fmt);
@@ -1630,6 +1624,9 @@ int bidirectional_transfer_loop(int input, int output)
{
struct bidirectional_transfer_state state;
+ if (transfer_debug_enabled < 0)
+ transfer_debug_enabled = getenv("GIT_TRANSLOOP_DEBUG") ? 1 : 0;
+
/* Fill the state fields. */
state.ptg.src = input;
state.ptg.dest = 1;