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Subject[PATCH 4.12 38/65] firmware: fix batched requests - wake all waiters
Date
4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Luis R. Rodriguez <mcgrof@kernel.org>

commit e44565f62a72064e686f7a852137595ec94d78f2 upstream.

The firmware cache mechanism serves two purposes, the secondary purpose is
not well documented nor understood. This fixes a regression with the
secondary purpose of the firmware cache mechanism: batched requests on
successful lookups. Without this fix *any* time a batched request is
triggered, secondary requests for which the batched request mechanism
was designed for will seem to last forver and seem to never return.
This issue is present for all kernel builds possible, and a hard reset
is required.

The firmware cache is used for:

1) Addressing races with file lookups during the suspend/resume cycle
by keeping firmware in memory during the suspend/resume cycle

2) Batched requests for the same file rely only on work from the first file
lookup, which keeps the firmware in memory until the last
release_firmware() is called

Batched requests *only* take effect if secondary requests come in prior to
the first user calling release_firmware(). The devres name used for the
internal firmware cache is used as a hint other pending requests are
ongoing, the firmware buffer data is kept in memory until the last user of
the buffer calls release_firmware(), therefore serializing requests and
delaying the release until all requests are done.

Batched requests wait for a wakup or signal so we can rely on the first file
fetch to write to the pending secondary requests. Commit 5b029624948d
("firmware: do not use fw_lock for fw_state protection") ported the firmware
API to use swait, and in doing so failed to convert complete_all() to
swake_up_all() -- it used swake_up(), loosing the ability for *some* batched
requests to take effect.

We *could* fix this by just using swake_up_all() *but* swait is now known
to be very special use case, so its best to just move away from it. So we
just go back to using completions as before commit 5b029624948d ("firmware:
do not use fw_lock for fw_state protection") given this was using
complete_all().

Without this fix it has been reported plugging in two Intel 6260 Wifi cards
on a system will end up enumerating the two devices only 50% of the time
[0]. The ported swake_up() should have actually handled the case with two
devices, however, *if more than two cards are used* the swake_up() would
not have sufficed. This change is only part of the required fixes for
batched requests. Another fix is provided in the next patch.

This particular change should fix the cases where more than three requests
with the same firmware name is used, otherwise batched requests will wait
for MAX_SCHEDULE_TIMEOUT and just timeout eventually.

Below is a summary of tests triggering batched requests on different
kernel builds.

Before this patch:
============================================================================
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=n
CONFIG_FW_LOADER_USER_HELPER=y

Most common Linux distribution setup.

API-type no-firmware-found firmware-found
----------------------------------------------------------------------
request_firmware() FAIL FAIL
request_firmware_direct() FAIL FAIL
request_firmware_nowait(uevent=true) FAIL FAIL
request_firmware_nowait(uevent=false) FAIL FAIL
============================================================================
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=n
CONFIG_FW_LOADER_USER_HELPER=n

Only possible if CONFIG_DELL_RBU=n and CONFIG_LEDS_LP55XX_COMMON=n, rare.

API-type no-firmware-found firmware-found
----------------------------------------------------------------------
request_firmware() FAIL FAIL
request_firmware_direct() FAIL FAIL
request_firmware_nowait(uevent=true) FAIL FAIL
request_firmware_nowait(uevent=false) FAIL FAIL
============================================================================
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
CONFIG_FW_LOADER_USER_HELPER=y

Google Android setup.

API-type no-firmware-found firmware-found
----------------------------------------------------------------------
request_firmware() FAIL FAIL
request_firmware_direct() FAIL FAIL
request_firmware_nowait(uevent=true) FAIL FAIL
request_firmware_nowait(uevent=false) FAIL FAIL
============================================================================

After this patch:
============================================================================
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=n
CONFIG_FW_LOADER_USER_HELPER=y

Most common Linux distribution setup.

API-type no-firmware-found firmware-found
----------------------------------------------------------------------
request_firmware() FAIL OK
request_firmware_direct() FAIL OK
request_firmware_nowait(uevent=true) FAIL OK
request_firmware_nowait(uevent=false) FAIL OK
============================================================================
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=n
CONFIG_FW_LOADER_USER_HELPER=n

Only possible if CONFIG_DELL_RBU=n and CONFIG_LEDS_LP55XX_COMMON=n, rare.

API-type no-firmware-found firmware-found
----------------------------------------------------------------------
request_firmware() FAIL OK
request_firmware_direct() FAIL OK
request_firmware_nowait(uevent=true) FAIL OK
request_firmware_nowait(uevent=false) FAIL OK
============================================================================
CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y
CONFIG_FW_LOADER_USER_HELPER=y

Google Android setup.

API-type no-firmware-found firmware-found
----------------------------------------------------------------------
request_firmware() OK OK
request_firmware_direct() FAIL OK
request_firmware_nowait(uevent=true) OK OK
request_firmware_nowait(uevent=false) OK OK
============================================================================

[0] https://bugzilla.kernel.org/show_bug.cgi?id=195477

Cc: Ming Lei <ming.lei@redhat.com>
Fixes: 5b029624948d ("firmware: do not use fw_lock for fw_state protection")
Reported-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/base/firmware_class.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)

--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -30,7 +30,6 @@
#include <linux/syscore_ops.h>
#include <linux/reboot.h>
#include <linux/security.h>
-#include <linux/swait.h>

#include <generated/utsrelease.h>

@@ -112,13 +111,13 @@ static inline long firmware_loading_time
* state of the firmware loading.
*/
struct fw_state {
- struct swait_queue_head wq;
+ struct completion completion;
enum fw_status status;
};

static void fw_state_init(struct fw_state *fw_st)
{
- init_swait_queue_head(&fw_st->wq);
+ init_completion(&fw_st->completion);
fw_st->status = FW_STATUS_UNKNOWN;
}

@@ -131,9 +130,8 @@ static int __fw_state_wait_common(struct
{
long ret;

- ret = swait_event_interruptible_timeout(fw_st->wq,
- __fw_state_is_done(READ_ONCE(fw_st->status)),
- timeout);
+ ret = wait_for_completion_interruptible_timeout(&fw_st->completion,
+ timeout);
if (ret != 0 && fw_st->status == FW_STATUS_ABORTED)
return -ENOENT;
if (!ret)
@@ -148,7 +146,7 @@ static void __fw_state_set(struct fw_sta
WRITE_ONCE(fw_st->status, status);

if (status == FW_STATUS_DONE || status == FW_STATUS_ABORTED)
- swake_up(&fw_st->wq);
+ complete_all(&fw_st->completion);
}

#define fw_state_start(fw_st) \

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