ESP32 Forum

f_getfree calls mount_volume, which calls get_ldnumber, which crashes in lock_volume, if no volume is mounted. The crash is due to an assertion failure of an uninitialized Mutex in xQueueSemaphoreTake, called by ff_mutex_take. Both Mutex[0] and FatFs[0] seem to have an invalid pointer at that time.

Hi @maierkomor,
I assume your code looks similar to the FatFS example on the elm-chan.org site:

FATFS *fs;
DWORD fre_clust, fre_sect, tot_sect;


/* Get volume information and free clusters of drive 1 */
res = f_getfree("1:", &fre_clust, &fs);
if (res) die(res);

/* Get total sectors and free sectors */
tot_sect = (fs->n_fatent - 2) * fs->csize;
fre_sect = fre_clust * fs->csize;

/* Print the free space (assuming 512 bytes/sector) */
printf("%10lu KiB total drive space.\n%10lu KiB available.\n", tot_sect / 2, fre_sect / 2);

We have to check the f_getfree() behaviour to confirm whether the issue comes from the IDF locks incorporation to the FatFS, or from the FatFS itself. Will keep you posted, thanks for the report!

Another hint for tracking the issue down. It might be the case that a mount attempt failed before calling the f_getfree. So it might be a case, of incomplete cleanup of the relevant data-structures after a failed mount attempt.