From: Daniel Wagner <[email protected]>
When we load the firmware directly we don't need to take the umh
lock(1). So move this part inside fw_load_from_user_helper which is only
available when CONFIG_FW_LOADER_USER_HELPER is set.
This avoids a dependency on firmware_loading_timeout() even when
!CONFIG_FW_LOADER_USER_HELPER. firmware_loading_timeout() will be moved
into the CONFIG_FW_LOADER_USER_HELPER section later.
The usermodehelper locking code was added by b298d289c792 ("PM / Sleep:
Fix freezer failures due to racy usermodehelper_is_disabled()").
(1) Luis analized this:
The original goal of the usermode helper lock came can be traced back in
time via a144c6a ("PM: Print a warning if firmware is requested when
task are frozen) when Rafael noticed drivers were calling to request
firmware on *resume* calls! Why would that be an issue? It was because
of the stupid delays incurred on resume when firmware *was not found*
__due__ to the stupid user mode helper timeout delay and people
believing this often meant users confusing resume *stalling* for resume
was *broken! Later b298d289c7
("PM / Sleep: Fix freezer failures due to racy
usermodehelper_is_disabled()") addressed races. That code in turn was
later massaged into shape to better accept direct FS loading via commit
4e0c92d015235 ("firmware: Refactoring for splitting user-mode helper
code").
So for a while we've been nagging driver developers to not add
request_firmware() calls on resume calls. In fact the
drivers/base/firmware_class.c code *kills* firmware UMH calls when we go
to suspend for the firmware cache, as such even on suspend its a stupid
idea to use the UMH, not only because it can stall suspend but *also*
because we kill these UMH calls.
[...]
So, as I see it the user mode helper lock should have *nothing* to do
with the race between reading files from the kernel and having a path
ready. If it was *used* for that, that was papering over the real
issue. Its no different of a hack for instance as if a driver using
request_firmware() tried to use async probe to avoid the same race. Yes
it will help, but no, it does not mean it is deterministically safe.
Reviewing commit 247bc03742545 ("PM / Sleep: Mitigate race between the freezer
and request_firmware()") which originally extended umh state machine from
just being enabled/disabled, with the concepts of UMH_ENABLED, UMH_FREEZING,
UMH_DISABLED -- its goal was to prevent UMH uses during suspend. So -- the
"UMH lock" on firmware was actually added to help avoid races between freezing
and request_firmware(). We should not re-use UMH status notifiers when the
firmware UMH is disabled for the same concepts -- if we needed such a concept
then we should take this out from UMH code and generalize it.
Signed-off-by: Daniel Wagner <[email protected]>
Cc: Ming Lei <[email protected]>
Cc: Luis R. Rodriguez <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
---
drivers/base/firmware_class.c | 52 +++++++++++++++++++++++--------------------
1 file changed, 28 insertions(+), 24 deletions(-)
diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 960f8f7c7aa2..d4fee06b67f3 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -981,13 +981,38 @@ static int fw_load_from_user_helper(struct firmware
*firmware,
unsigned int opt_flags, long timeout)
{
struct firmware_priv *fw_priv;
+ int ret;
+
+ timeout = firmware_loading_timeout();
+ if (opt_flags & FW_OPT_NOWAIT) {
+ timeout = usermodehelper_read_lock_wait(timeout);
+ if (!timeout) {
+ dev_dbg(device, "firmware: %s loading timed out\n",
+ name);
+ return -EBUSY;
+ }
+ } else {
+ ret = usermodehelper_read_trylock();
+ if (WARN_ON(ret)) {
+ dev_err(device, "firmware: %s will not be loaded\n",
+ name);
+ return ret;
+ }
+ }
fw_priv = fw_create_instance(firmware, name, device, opt_flags);
- if (IS_ERR(fw_priv))
- return PTR_ERR(fw_priv);
+ if (IS_ERR(fw_priv)) {
+ ret = PTR_ERR(fw_priv);
+ goto release_lock;
+ }
fw_priv->buf = firmware->priv;
- return _request_firmware_load(fw_priv, opt_flags, timeout);
+ ret = _request_firmware_load(fw_priv, opt_flags, timeout);
+
+release_lock:
+ usermodehelper_read_unlock();
+
+ return ret;
}
#ifdef CONFIG_PM_SLEEP
@@ -1150,25 +1175,6 @@ _request_firmware(const struct firmware **firmware_p,
const char *name,
if (ret <= 0) /* error or already assigned */
goto out;
- ret = 0;
- timeout = firmware_loading_timeout();
- if (opt_flags & FW_OPT_NOWAIT) {
- timeout = usermodehelper_read_lock_wait(timeout);
- if (!timeout) {
- dev_dbg(device, "firmware: %s loading timed out\n",
- name);
- ret = -EBUSY;
- goto out;
- }
- } else {
- ret = usermodehelper_read_trylock();
- if (WARN_ON(ret)) {
- dev_err(device, "firmware: %s will not be loaded\n",
- name);
- goto out;
- }
- }
-
ret = fw_get_filesystem_firmware(device, fw->priv);
if (ret) {
if (!(opt_flags & FW_OPT_NO_WARN))
@@ -1185,8 +1191,6 @@ _request_firmware(const struct firmware **firmware_p,
const char *name,
if (!ret)
ret = assign_firmware_buf(fw, device, opt_flags);
- usermodehelper_read_unlock();
-
out:
if (ret < 0) {
release_firmware(fw);
--
2.7.4
