Commit 9c0f59e4 authored by Nam Cao's avatar Nam Cao Committed by Jiri Kosina

HID: i2c-hid: remove I2C_HID_READ_PENDING flag to prevent lock-up

The flag I2C_HID_READ_PENDING is used to serialize I2C operations.
However, this is not necessary, because I2C core already has its own
locking for that.

More importantly, this flag can cause a lock-up: if the flag is set in
i2c_hid_xfer() and an interrupt happens, the interrupt handler
(i2c_hid_irq) will check this flag and return immediately without doing
anything, then the interrupt handler will be invoked again in an
infinite loop.

Since interrupt handler is an RT task, it takes over the CPU and the
flag-clearing task never gets scheduled, thus we have a lock-up.

Delete this unnecessary flag.
Reported-and-tested-by: default avatarEva Kurchatova <nyandarknessgirl@gmail.com>
Closes: https://lore.kernel.org/r/CA+eeCSPUDpUg76ZO8dszSbAGn+UHjcyv8F1J-CUPVARAzEtW9w@mail.gmail.com
Fixes: 4a200c3b ("HID: i2c-hid: introduce HID over i2c specification implementation")
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarNam Cao <namcao@linutronix.de>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.com>
parent 3e78a6c0
...@@ -64,7 +64,6 @@ ...@@ -64,7 +64,6 @@
/* flags */ /* flags */
#define I2C_HID_STARTED 0 #define I2C_HID_STARTED 0
#define I2C_HID_RESET_PENDING 1 #define I2C_HID_RESET_PENDING 1
#define I2C_HID_READ_PENDING 2
#define I2C_HID_PWR_ON 0x00 #define I2C_HID_PWR_ON 0x00
#define I2C_HID_PWR_SLEEP 0x01 #define I2C_HID_PWR_SLEEP 0x01
...@@ -190,15 +189,10 @@ static int i2c_hid_xfer(struct i2c_hid *ihid, ...@@ -190,15 +189,10 @@ static int i2c_hid_xfer(struct i2c_hid *ihid,
msgs[n].len = recv_len; msgs[n].len = recv_len;
msgs[n].buf = recv_buf; msgs[n].buf = recv_buf;
n++; n++;
set_bit(I2C_HID_READ_PENDING, &ihid->flags);
} }
ret = i2c_transfer(client->adapter, msgs, n); ret = i2c_transfer(client->adapter, msgs, n);
if (recv_len)
clear_bit(I2C_HID_READ_PENDING, &ihid->flags);
if (ret != n) if (ret != n)
return ret < 0 ? ret : -EIO; return ret < 0 ? ret : -EIO;
...@@ -556,9 +550,6 @@ static irqreturn_t i2c_hid_irq(int irq, void *dev_id) ...@@ -556,9 +550,6 @@ static irqreturn_t i2c_hid_irq(int irq, void *dev_id)
{ {
struct i2c_hid *ihid = dev_id; struct i2c_hid *ihid = dev_id;
if (test_bit(I2C_HID_READ_PENDING, &ihid->flags))
return IRQ_HANDLED;
i2c_hid_get_input(ihid); i2c_hid_get_input(ihid);
return IRQ_HANDLED; return IRQ_HANDLED;
......
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