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authorDuoming Zhou <duoming@zju.edu.cn>2022-04-07 23:44:30 +0800
committerMax Filippov <jcmvbkbc@gmail.com>2022-04-13 03:36:34 -0700
commiteb5adc70754d26a260f8b42d39db42da0d0af500 (patch)
tree9ec355723ab991c97f26a64c195382d1f0bec852 /arch/xtensa
parentee69d4be8fd064cd08270b4808d2dfece3614ee0 (diff)
arch: xtensa: platforms: Fix deadlock in rs_close()
There is a deadlock in rs_close(), which is shown below: (Thread 1) | (Thread 2) | rs_open() rs_close() | mod_timer() spin_lock_bh() //(1) | (wait a time) ... | rs_poll() del_timer_sync() | spin_lock() //(2) (wait timer to stop) | ... We hold timer_lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need timer_lock in position (2) of thread 2. As a result, rs_close() will block forever. This patch deletes the redundant timer_lock in order to prevent the deadlock. Because there is no race condition between rs_close, rs_open and rs_poll. Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Message-Id: <20220407154430.22387-1-duoming@zju.edu.cn> Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Diffstat (limited to 'arch/xtensa')
-rw-r--r--arch/xtensa/platforms/iss/console.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/arch/xtensa/platforms/iss/console.c b/arch/xtensa/platforms/iss/console.c
index 81d7c7e8f7e9..10b79d3c74e0 100644
--- a/arch/xtensa/platforms/iss/console.c
+++ b/arch/xtensa/platforms/iss/console.c
@@ -36,24 +36,19 @@ static void rs_poll(struct timer_list *);
static struct tty_driver *serial_driver;
static struct tty_port serial_port;
static DEFINE_TIMER(serial_timer, rs_poll);
-static DEFINE_SPINLOCK(timer_lock);
static int rs_open(struct tty_struct *tty, struct file * filp)
{
- spin_lock_bh(&timer_lock);
if (tty->count == 1)
mod_timer(&serial_timer, jiffies + SERIAL_TIMER_VALUE);
- spin_unlock_bh(&timer_lock);
return 0;
}
static void rs_close(struct tty_struct *tty, struct file * filp)
{
- spin_lock_bh(&timer_lock);
if (tty->count == 1)
del_timer_sync(&serial_timer);
- spin_unlock_bh(&timer_lock);
}
@@ -73,8 +68,6 @@ static void rs_poll(struct timer_list *unused)
int rd = 1;
unsigned char c;
- spin_lock(&timer_lock);
-
while (simc_poll(0)) {
rd = simc_read(0, &c, 1);
if (rd <= 0)
@@ -87,7 +80,6 @@ static void rs_poll(struct timer_list *unused)
tty_flip_buffer_push(port);
if (rd)
mod_timer(&serial_timer, jiffies + SERIAL_TIMER_VALUE);
- spin_unlock(&timer_lock);
}