On Thu, Aug 15, 2019 at 05:09:45PM -0700, Scott Branden wrote: > A race condition exists between _request_firmware_prepare checking > if firmware is assigned and firmware_fallback_sysfs creating a sysfs > entry (kernel trace below). To avoid such condition add a mutex > fw_lock_fallback to protect against such condition. I am not buying this fix, and it seems sloppy. More below. > misc test_firmware: Falling back to sysfs fallback for: nope-test-firmware.bin So the fallback kicks in with the file that is not there. > sysfs: cannot create duplicate filename '/devices/virtual/misc/test_firmware/nope-test-firmware.bin' And we have a duplicate entry, for the *device* created to allow us to create a file entry to allow us to copy the file. Your tests had a loop, so there is actually a race between two entries being created while one one failed. > CPU: 4 PID: 2059 Comm: test_firmware-3 Not tainted 5.3.0-rc4 #1 > Hardware name: Dell Inc. OptiPlex 7010/0KRC95, BIOS A13 03/25/2013 > Call Trace: > dump_stack+0x67/0x90 > sysfs_warn_dup.cold+0x17/0x24 > sysfs_create_dir_ns+0xb3/0xd0 > kobject_add_internal+0xa6/0x2a0 > kobject_add+0x7e/0xb0 Note: kobject_add(). > ? _cond_resched+0x15/0x30 > device_add+0x121/0x670 > firmware_fallback_sysfs+0x15c/0x3c9 > _request_firmware+0x432/0x5a0 > ? devres_find+0x63/0xc0 > request_firmware_into_buf+0x63/0x80 > test_fw_run_batch_request+0x96/0xe0 > kthread+0xfb/0x130 > ? reset_store+0x30/0x30 > ? kthread_park+0x80/0x80 > ret_from_fork+0x3a/0x50 > kobject_add_internal failed for nope-test-firmware.bin with -EEXIST, don't try to register things with the same name in the same directory. So above it makes it even clearer, two kobjets with the same name. > Signed-off-by: Scott Branden <scott.branden@xxxxxxxxxxxx> > --- > drivers/base/firmware_loader/main.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c > index bf44c79beae9..ce9896e3b782 100644 > --- a/drivers/base/firmware_loader/main.c > +++ b/drivers/base/firmware_loader/main.c > @@ -88,6 +88,7 @@ static inline struct fw_priv *to_fw_priv(struct kref *ref) > /* fw_lock could be moved to 'struct fw_sysfs' but since it is just > * guarding for corner cases a global lock should be OK */ > DEFINE_MUTEX(fw_lock); > +DEFINE_MUTEX(fw_lock_fallback); The reason I don't like this fix is that this mutex is named after ther fallback interface... but... > > static struct firmware_cache fw_cache; > > @@ -758,6 +759,17 @@ _request_firmware(const struct firmware **firmware_p, const char *name, > if (!firmware_p) > return -EINVAL; > > + /* > + * There is a race condition between _request_firmware_prepare checking > + * if firmware is assigned and firmware_fallback_sysfs creating sysfs > + * entries with duplicate names. > + * Yet, with this lock the firmware_test locks up with cache enabled > + * and no event used during firmware test. > + * This points to some very racy code I don't know how to entirely fix. > + */ > + if (opt_flags & FW_OPT_NOCACHE) > + mutex_lock(&fw_lock_fallback); Whoa.. What does no-cache have anything to do with the fallback interface other than the fact we enable this feature for the fallback interface? We don't need to penalize non-fallback users who *also* may want to enable the no-cache feature. So, the fix should be within the boundaries of the creation / deletion of the kobject, not this nocache feature. Can you please re-evaluate this code and look for a more compartamentalized solution to the fallback code only? Luis
