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transport-helper: fix TSAN race in transfer_debug()

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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>
This commit is contained in:
Pushkar Singh
2026-06-09 13:47:42 +00:00
committed by Junio C Hamano
parent a89346e34a
commit 85704eda18
2 changed files with 8 additions and 12 deletions
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1
.tsan-suppressions
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@@ -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,

19
transport-helper.c
View File

@@ -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;