This is a note to let you know that I've just added the patch titled
scsi: ufs: core: Fix devfreq deadlocks
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
scsi-ufs-core-fix-devfreq-deadlocks.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f90533938563343b53eca6629f1cf99332a5e1d8
Author: Johan Hovold <johan+linaro@xxxxxxxxxx>
Date: Mon Jan 16 17:12:01 2023 +0100
scsi: ufs: core: Fix devfreq deadlocks
[ Upstream commit ba81043753fffbc2ad6e0c5ff2659f12ac2f46b4 ]
There is a lock inversion and rwsem read-lock recursion in the devfreq
target callback which can lead to deadlocks.
Specifically, ufshcd_devfreq_scale() already holds a clk_scaling_lock
read lock when toggling the write booster, which involves taking the
dev_cmd mutex before taking another clk_scaling_lock read lock.
This can lead to a deadlock if another thread:
1) tries to acquire the dev_cmd and clk_scaling locks in the correct
order, or
2) takes a clk_scaling write lock before the attempt to take the
clk_scaling read lock a second time.
Fix this by dropping the clk_scaling_lock before toggling the write booster
as was done before commit 0e9d4ca43ba8 ("scsi: ufs: Protect some contexts
from unexpected clock scaling").
While the devfreq callbacks are already serialised, add a second
serialising mutex to handle the unlikely case where a callback triggered
through the devfreq sysfs interface is racing with a request to disable
clock scaling through the UFS controller 'clkscale_enable' sysfs
attribute. This could otherwise lead to the write booster being left
disabled after having disabled clock scaling.
Also take the new mutex in ufshcd_clk_scaling_allow() to make sure that any
pending write booster update has completed on return.
Note that this currently only affects Qualcomm platforms since commit
87bd05016a64 ("scsi: ufs: core: Allow host driver to disable wb toggling
during clock scaling").
The lock inversion (i.e. 1 above) was reported by lockdep as:
======================================================
WARNING: possible circular locking dependency detected
6.1.0-next-20221216 #211 Not tainted
------------------------------------------------------
kworker/u16:2/71 is trying to acquire lock:
ffff076280ba98a0 (&hba->dev_cmd.lock){+.+.}-{3:3}, at: ufshcd_query_flag+0x50/0x1c0
but task is already holding lock:
ffff076280ba9cf0 (&hba->clk_scaling_lock){++++}-{3:3}, at: ufshcd_devfreq_scale+0x2b8/0x380
which lock already depends on the new lock.
[ +0.011606]
the existing dependency chain (in reverse order) is:
-> #1 (&hba->clk_scaling_lock){++++}-{3:3}:
lock_acquire+0x68/0x90
down_read+0x58/0x80
ufshcd_exec_dev_cmd+0x70/0x2c0
ufshcd_verify_dev_init+0x68/0x170
ufshcd_probe_hba+0x398/0x1180
ufshcd_async_scan+0x30/0x320
async_run_entry_fn+0x34/0x150
process_one_work+0x288/0x6c0
worker_thread+0x74/0x450
kthread+0x118/0x120
ret_from_fork+0x10/0x20
-> #0 (&hba->dev_cmd.lock){+.+.}-{3:3}:
__lock_acquire+0x12a0/0x2240
lock_acquire.part.0+0xcc/0x220
lock_acquire+0x68/0x90
__mutex_lock+0x98/0x430
mutex_lock_nested+0x2c/0x40
ufshcd_query_flag+0x50/0x1c0
ufshcd_query_flag_retry+0x64/0x100
ufshcd_wb_toggle+0x5c/0x120
ufshcd_devfreq_scale+0x2c4/0x380
ufshcd_devfreq_target+0xf4/0x230
devfreq_set_target+0x84/0x2f0
devfreq_update_target+0xc4/0xf0
devfreq_monitor+0x38/0x1f0
process_one_work+0x288/0x6c0
worker_thread+0x74/0x450
kthread+0x118/0x120
ret_from_fork+0x10/0x20
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&hba->clk_scaling_lock);
lock(&hba->dev_cmd.lock);
lock(&hba->clk_scaling_lock);
lock(&hba->dev_cmd.lock);
*** DEADLOCK ***
Fixes: 0e9d4ca43ba8 ("scsi: ufs: Protect some contexts from unexpected clock scaling")
Cc: stable@xxxxxxxxxxxxxxx # 5.12
Cc: Can Guo <quic_cang@xxxxxxxxxxx>
Tested-by: Andrew Halaney <ahalaney@xxxxxxxxxx>
Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Link: https://lore.kernel.org/r/20230116161201.16923-1-johan+linaro@xxxxxxxxxx
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 0b06223f5714..120831428ec6 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1185,12 +1185,14 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
* clock scaling is in progress
*/
ufshcd_scsi_block_requests(hba);
+ mutex_lock(&hba->wb_mutex);
down_write(&hba->clk_scaling_lock);
if (!hba->clk_scaling.is_allowed ||
ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
ret = -EBUSY;
up_write(&hba->clk_scaling_lock);
+ mutex_unlock(&hba->wb_mutex);
ufshcd_scsi_unblock_requests(hba);
goto out;
}
@@ -1202,12 +1204,15 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
return ret;
}
-static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock)
+static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, int err, bool scale_up)
{
- if (writelock)
- up_write(&hba->clk_scaling_lock);
- else
- up_read(&hba->clk_scaling_lock);
+ up_write(&hba->clk_scaling_lock);
+
+ /* Enable Write Booster if we have scaled up else disable it */
+ ufshcd_wb_toggle(hba, scale_up);
+
+ mutex_unlock(&hba->wb_mutex);
+
ufshcd_scsi_unblock_requests(hba);
ufshcd_release(hba);
}
@@ -1224,7 +1229,6 @@ static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba, bool writelock)
static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
{
int ret = 0;
- bool is_writelock = true;
ret = ufshcd_clock_scaling_prepare(hba);
if (ret)
@@ -1253,13 +1257,8 @@ static int ufshcd_devfreq_scale(struct ufs_hba *hba, bool scale_up)
}
}
- /* Enable Write Booster if we have scaled up else disable it */
- downgrade_write(&hba->clk_scaling_lock);
- is_writelock = false;
- ufshcd_wb_toggle(hba, scale_up);
-
out_unprepare:
- ufshcd_clock_scaling_unprepare(hba, is_writelock);
+ ufshcd_clock_scaling_unprepare(hba, ret, scale_up);
return ret;
}
@@ -5919,9 +5918,11 @@ static void ufshcd_force_error_recovery(struct ufs_hba *hba)
static void ufshcd_clk_scaling_allow(struct ufs_hba *hba, bool allow)
{
+ mutex_lock(&hba->wb_mutex);
down_write(&hba->clk_scaling_lock);
hba->clk_scaling.is_allowed = allow;
up_write(&hba->clk_scaling_lock);
+ mutex_unlock(&hba->wb_mutex);
}
static void ufshcd_clk_scaling_suspend(struct ufs_hba *hba, bool suspend)
@@ -9480,6 +9481,7 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
/* Initialize mutex for exception event control */
mutex_init(&hba->ee_ctrl_mutex);
+ mutex_init(&hba->wb_mutex);
init_rwsem(&hba->clk_scaling_lock);
ufshcd_init_clk_gating(hba);
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index d470a52ff24c..c8513cc6c2bd 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -763,6 +763,7 @@ struct ufs_hba_monitor {
* @urgent_bkops_lvl: keeps track of urgent bkops level for device
* @is_urgent_bkops_lvl_checked: keeps track if the urgent bkops level for
* device is known or not.
+ * @wb_mutex: used to serialize devfreq and sysfs write booster toggling
* @scsi_block_reqs_cnt: reference counting for scsi block requests
* @crypto_capabilities: Content of crypto capabilities register (0x100)
* @crypto_cap_array: Array of crypto capabilities
@@ -892,6 +893,7 @@ struct ufs_hba {
enum bkops_status urgent_bkops_lvl;
bool is_urgent_bkops_lvl_checked;
+ struct mutex wb_mutex;
struct rw_semaphore clk_scaling_lock;
unsigned char desc_size[QUERY_DESC_IDN_MAX];
atomic_t scsi_block_reqs_cnt;
