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memdebug: add mutex for thread safety

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Protect modification to the `membuf` by different threads
via a mutex. This ensure that index updates are correct and
that data gets written in order.

Closes #19785
This commit is contained in:
Stefan Eissing 2025-12-01 13:22:25 +01:00 committed by Daniel Stenberg
parent c6c4a99300
commit a7bebd8502
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1 changed files with 27 additions and 0 deletions
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27
lib/memdebug.c
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@ -29,6 +29,7 @@
#include <curl/curl.h>
#include "urldata.h"
#include "curl_threads.h"
#include "curlx/fopen.h" /* for CURLX_FOPEN_LOW(), CURLX_FREOPEN_LOW() */
#ifdef USE_BACKTRACE
@ -66,6 +67,11 @@ static struct backtrace_state *btstate;
static char membuf[KEEPSIZE];
static size_t memwidx = 0; /* write index */
#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
static bool dbg_mutex_init = 0;
static curl_mutex_t dbg_mutex;
#endif
/* LeakSantizier (LSAN) calls _exit() instead of exit() when a leak is detected
on exit so the logfile must be closed explicitly or data could be lost.
Though _exit() does not call atexit handlers such as this, LSAN's call to
@ -81,6 +87,12 @@ static void curl_dbg_cleanup(void)
fclose(curl_dbg_logfile);
}
curl_dbg_logfile = NULL;
#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
if(dbg_mutex_init) {
Curl_mutex_destroy(&dbg_mutex);
dbg_mutex_init = FALSE;
}
#endif
}
#ifdef USE_BACKTRACE
static void error_bt_callback(void *data, const char *message,
@ -123,6 +135,12 @@ void curl_dbg_memdebug(const char *logname)
setbuf(curl_dbg_logfile, (char *)NULL);
#endif
}
#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
if(!dbg_mutex_init) {
dbg_mutex_init = TRUE;
Curl_mutex_init(&dbg_mutex);
}
#endif
#ifdef USE_BACKTRACE
btstate = backtrace_create_state(NULL, 0, error_bt_callback, NULL);
#endif
@ -526,6 +544,11 @@ void curl_dbg_log(const char *format, ...)
nchars = (int)sizeof(buf) - 1;
if(nchars > 0) {
#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
bool lock_mutex = dbg_mutex_init;
if(lock_mutex)
Curl_mutex_acquire(&dbg_mutex);
#endif
if(KEEPSIZE - nchars < memwidx) {
/* flush */
fwrite(membuf, 1, memwidx, curl_dbg_logfile);
@ -538,6 +561,10 @@ void curl_dbg_log(const char *format, ...)
}
memcpy(&membuf[memwidx], buf, nchars);
memwidx += nchars;
#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
if(lock_mutex)
Curl_mutex_release(&dbg_mutex);
#endif
}
}