Revert "tty: n_gsm: avoid call of sleeping functions from atomic context"

commit acdab4cb4ba7e5f94d2b422ebd7bf4bf68178fb2 upstream.

This reverts commit 902e02ea9385373ce4b142576eef41c642703955.

The above commit is reverted as the usage of tx_mutex seems not to solve
the problem described in 902e02ea9385 ("tty: n_gsm: avoid call of sleeping
functions from atomic context") and just moves the bug to another place.

Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Reviewed-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20221008110221.13645-2-pchelkin@ispras.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index e8528282597357229ece7e08b01c3a93d68cd764..f5063499f9cf68d934b5f4a80a166858076e1e7c 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -235,7 +235,7 @@ struct gsm_mux {
        int old_c_iflag;                /* termios c_iflag value before attach */
        bool constipated;               /* Asked by remote to shut up */
 
-       struct mutex tx_mutex;
+       spinlock_t tx_lock;
        unsigned int tx_bytes;          /* TX data outstanding */
 #define TX_THRESH_HI           8192
 #define TX_THRESH_LO           2048
@@ -820,14 +820,15 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
  *
  *     Add data to the transmit queue and try and get stuff moving
  *     out of the mux tty if not already doing so. Take the
- *     the gsm tx mutex and dlci lock.
+ *     the gsm tx lock and dlci lock.
  */
 
 static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 {
-       mutex_lock(&dlci->gsm->tx_mutex);
+       unsigned long flags;
+       spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
        __gsm_data_queue(dlci, msg);
-       mutex_unlock(&dlci->gsm->tx_mutex);
+       spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
 }
 
 /**
@@ -839,7 +840,7 @@ static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
  *     is data. Keep to the MRU of the mux. This path handles the usual tty
  *     interface which is a byte stream with optional modem data.
  *
- *     Caller must hold the tx_mutex of the mux.
+ *     Caller must hold the tx_lock of the mux.
  */
 
 static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
@@ -902,7 +903,7 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
  *     is data. Keep to the MRU of the mux. This path handles framed data
  *     queued as skbuffs to the DLCI.
  *
- *     Caller must hold the tx_mutex of the mux.
+ *     Caller must hold the tx_lock of the mux.
  */
 
 static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
@@ -918,7 +919,7 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
        if (dlci->adaption == 4)
                overhead = 1;
 
-       /* dlci->skb is locked by tx_mutex */
+       /* dlci->skb is locked by tx_lock */
        if (dlci->skb == NULL) {
                dlci->skb = skb_dequeue_tail(&dlci->skb_list);
                if (dlci->skb == NULL)
@@ -1018,12 +1019,13 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
 
 static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
 {
+       unsigned long flags;
        int sweep;
 
        if (dlci->constipated)
                return;
 
-       mutex_lock(&dlci->gsm->tx_mutex);
+       spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
        /* If we have nothing running then we need to fire up */
        sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO);
        if (dlci->gsm->tx_bytes == 0) {
@@ -1034,7 +1036,7 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
        }
        if (sweep)
                gsm_dlci_data_sweep(dlci->gsm);
-       mutex_unlock(&dlci->gsm->tx_mutex);
+       spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
 }
 
 /*
@@ -1256,6 +1258,7 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
                                                const u8 *data, int clen)
 {
        u8 buf[1];
+       unsigned long flags;
 
        switch (command) {
        case CMD_CLD: {
@@ -1277,9 +1280,9 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
                gsm->constipated = false;
                gsm_control_reply(gsm, CMD_FCON, NULL, 0);
                /* Kick the link in case it is idling */
-               mutex_lock(&gsm->tx_mutex);
+               spin_lock_irqsave(&gsm->tx_lock, flags);
                gsm_data_kick(gsm, NULL);
-               mutex_unlock(&gsm->tx_mutex);
+               spin_unlock_irqrestore(&gsm->tx_lock, flags);
                break;
        case CMD_FCOFF:
                /* Modem wants us to STFU */
@@ -2225,7 +2228,6 @@ static void gsm_free_mux(struct gsm_mux *gsm)
                        break;
                }
        }
-       mutex_destroy(&gsm->tx_mutex);
        mutex_destroy(&gsm->mutex);
        kfree(gsm->txframe);
        kfree(gsm->buf);
@@ -2297,12 +2299,12 @@ static struct gsm_mux *gsm_alloc_mux(void)
        }
        spin_lock_init(&gsm->lock);
        mutex_init(&gsm->mutex);
-       mutex_init(&gsm->tx_mutex);
        kref_init(&gsm->ref);
        INIT_LIST_HEAD(&gsm->tx_list);
        timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
        init_waitqueue_head(&gsm->event);
        spin_lock_init(&gsm->control_lock);
+       spin_lock_init(&gsm->tx_lock);
 
        gsm->t1 = T1;
        gsm->t2 = T2;
@@ -2327,7 +2329,6 @@ static struct gsm_mux *gsm_alloc_mux(void)
        }
        spin_unlock(&gsm_mux_lock);
        if (i == MAX_MUX) {
-               mutex_destroy(&gsm->tx_mutex);
                mutex_destroy(&gsm->mutex);
                kfree(gsm->txframe);
                kfree(gsm->buf);
@@ -2652,15 +2653,16 @@ static int gsmld_open(struct tty_struct *tty)
 static void gsmld_write_wakeup(struct tty_struct *tty)
 {
        struct gsm_mux *gsm = tty->disc_data;
+       unsigned long flags;
 
        /* Queue poll */
        clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
-       mutex_lock(&gsm->tx_mutex);
+       spin_lock_irqsave(&gsm->tx_lock, flags);
        gsm_data_kick(gsm, NULL);
        if (gsm->tx_bytes < TX_THRESH_LO) {
                gsm_dlci_data_sweep(gsm);
        }
-       mutex_unlock(&gsm->tx_mutex);
+       spin_unlock_irqrestore(&gsm->tx_lock, flags);
 }
 
 /**
@@ -2703,6 +2705,7 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
                           const unsigned char *buf, size_t nr)
 {
        struct gsm_mux *gsm = tty->disc_data;
+       unsigned long flags;
        int space;
        int ret;
 
@@ -2710,13 +2713,13 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
                return -ENODEV;
 
        ret = -ENOBUFS;
-       mutex_lock(&gsm->tx_mutex);
+       spin_lock_irqsave(&gsm->tx_lock, flags);
        space = tty_write_room(tty);
        if (space >= nr)
                ret = tty->ops->write(tty, buf, nr);
        else
                set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
-       mutex_unlock(&gsm->tx_mutex);
+       spin_unlock_irqrestore(&gsm->tx_lock, flags);
 
        return ret;
 }