From: Björn Ardö bjorn.ardo@axis.com
[ Upstream commit bca1a1004615efe141fd78f360ecc48c60bc4ad5 ]
This reverts commit c7dacf5b0f32957b24ef29df1207dc2cd8307743, "mailbox: avoid timer start from callback"
The previous commit was reverted since it lead to a race that caused the hrtimer to not be started at all. The check for hrtimer_active() in msg_submit() will return true if the callback function txdone_hrtimer() is currently running. This function could return HRTIMER_NORESTART and then the timer will not be restarted, and also msg_submit() will not start the timer. This will lead to a message actually being submitted but no timer will start to check for its compleation.
The original fix that added checking hrtimer_active() was added to avoid a warning with hrtimer_forward. Looking in the kernel another solution to avoid this warning is to check hrtimer_is_queued() before calling hrtimer_forward_now() instead. This however requires a lock so the timer is not started by msg_submit() inbetween this check and the hrtimer_forward() call.
Fixes: c7dacf5b0f32 ("mailbox: avoid timer start from callback") Signed-off-by: Björn Ardö bjorn.ardo@axis.com Signed-off-by: Jassi Brar jaswinder.singh@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/mailbox/mailbox.c | 19 +++++++++++++------ include/linux/mailbox_controller.h | 1 + 2 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c index 3e7d4b20ab34..4229b9b5da98 100644 --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -82,11 +82,11 @@ static void msg_submit(struct mbox_chan *chan) exit: spin_unlock_irqrestore(&chan->lock, flags);
- /* kick start the timer immediately to avoid delays */ if (!err && (chan->txdone_method & TXDONE_BY_POLL)) { - /* but only if not already active */ - if (!hrtimer_active(&chan->mbox->poll_hrt)) - hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); + /* kick start the timer immediately to avoid delays */ + spin_lock_irqsave(&chan->mbox->poll_hrt_lock, flags); + hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); + spin_unlock_irqrestore(&chan->mbox->poll_hrt_lock, flags); } }
@@ -120,20 +120,26 @@ static enum hrtimer_restart txdone_hrtimer(struct hrtimer *hrtimer) container_of(hrtimer, struct mbox_controller, poll_hrt); bool txdone, resched = false; int i; + unsigned long flags;
for (i = 0; i < mbox->num_chans; i++) { struct mbox_chan *chan = &mbox->chans[i];
if (chan->active_req && chan->cl) { - resched = true; txdone = chan->mbox->ops->last_tx_done(chan); if (txdone) tx_tick(chan, 0); + else + resched = true; } }
if (resched) { - hrtimer_forward_now(hrtimer, ms_to_ktime(mbox->txpoll_period)); + spin_lock_irqsave(&mbox->poll_hrt_lock, flags); + if (!hrtimer_is_queued(hrtimer)) + hrtimer_forward_now(hrtimer, ms_to_ktime(mbox->txpoll_period)); + spin_unlock_irqrestore(&mbox->poll_hrt_lock, flags); + return HRTIMER_RESTART; } return HRTIMER_NORESTART; @@ -500,6 +506,7 @@ int mbox_controller_register(struct mbox_controller *mbox) hrtimer_init(&mbox->poll_hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); mbox->poll_hrt.function = txdone_hrtimer; + spin_lock_init(&mbox->poll_hrt_lock); }
for (i = 0; i < mbox->num_chans; i++) { diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_controller.h index 36d6ce673503..6fee33cb52f5 100644 --- a/include/linux/mailbox_controller.h +++ b/include/linux/mailbox_controller.h @@ -83,6 +83,7 @@ struct mbox_controller { const struct of_phandle_args *sp); /* Internal to API */ struct hrtimer poll_hrt; + spinlock_t poll_hrt_lock; struct list_head node; };