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serial/pty: Don't use shced_[lock|unlock] to protect pp_locked

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since the sched lock can't work in SMP context

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
This commit is contained in:
Xiang Xiao 2022-02-07 00:29:04 +08:00 committed by Alan Carvalho de Assis
parent f03fc4a179
commit e3fed03e43
1 changed files with 33 additions and 58 deletions
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91
drivers/serial/pty.c
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@ -278,20 +278,28 @@ static int pty_open(FAR struct file *filep)
DEBUGASSERT(dev != NULL && dev->pd_devpair != NULL);
devpair = dev->pd_devpair;
/* Get exclusive access to the device structure */
ret = pty_semtake(devpair);
if (ret < 0)
{
return ret;
}
/* Wait if this is an attempt to open the slave device and the slave
* device is locked.
*/
if (!dev->pd_master)
{
/* Slave... Check if the slave driver is locked. We need to lock the
* scheduler while we are running to prevent asyncrhonous modification
* of pp_locked by pty_ioctl().
*/
/* Slave... Check if the slave driver is locked. */
sched_lock();
while (devpair->pp_locked)
{
/* Release the exclusive access before wait */
pty_semgive(devpair);
/* Wait until unlocked.
* We will also most certainly suspend here.
*/
@ -299,10 +307,13 @@ static int pty_open(FAR struct file *filep)
ret = nxsem_wait(&devpair->pp_slavesem);
if (ret < 0)
{
sched_unlock();
return ret;
}
/* Restore the semaphore count */
DEBUGVERIFY(nxsem_post(&devpair->pp_slavesem));
/* Get exclusive access to the device structure. This might also
* cause suspension.
*/
@ -310,35 +321,8 @@ static int pty_open(FAR struct file *filep)
ret = pty_semtake(devpair);
if (ret < 0)
{
sched_unlock();
return ret;
}
/* Check again in case something happened asynchronously while we
* were suspended.
*/
if (devpair->pp_locked)
{
/* This cannot suspend because we have the scheduler locked.
* So pp_locked cannot change asyncrhonously between this test
* and the redundant test at the top of the loop.
*/
pty_semgive(devpair);
}
}
sched_unlock();
}
else
{
/* Master ... Get exclusive access to the device structure */
ret = pty_semtake(devpair);
if (ret < 0)
{
return ret;
}
}
@ -785,35 +769,26 @@ static int pty_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
if (arg == 0)
{
int sval;
if (devpair->pp_locked)
{
/* Release any waiting threads */
/* Unlocking */
sched_lock();
devpair->pp_locked = false;
/* Release any waiting threads */
do
{
DEBUGVERIFY(nxsem_get_value(&devpair->pp_slavesem,
&sval));
if (sval < 0)
{
nxsem_post(&devpair->pp_slavesem);
}
}
while (sval < 0);
sched_unlock();
ret = OK;
ret = nxsem_post(&devpair->pp_slavesem);
if (ret >= 0)
{
devpair->pp_locked = false;
}
}
}
else
else if (!devpair->pp_locked)
{
/* Locking */
devpair->pp_locked = true;
ret = OK;
ret = nxsem_wait(&devpair->pp_slavesem);
if (ret >= 0)
{
devpair->pp_locked = true;
}
}
}
break;
@ -827,7 +802,7 @@ static int pty_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
}
else
{
*ptr = (int)devpair->pp_locked;
*ptr = devpair->pp_locked;
ret = OK;
}
}