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Thomas Gleixner authored
commit d2e6d62c upstream. commit c58d80f5 ("usb: musb: Ensure that cppi41 timer gets armed on premature DMA TX irq") fixed hrtimer scheduling bug. There is one left which does not trigger that often. The following scenario is still possible: lock(&x->lock); hrtimer_start(&x->t); unlock(&x->lock); expires: t->function(); lock(&x->lock); lock(&x->lock); if (!hrtimer_queued(&x->t)) hrtimer_start(&x->t); unlock(&x->lock); if (!list_empty(x->early_tx_list)) ret = HRTIMER_RESTART; -> hrtimer_forward_now(...) } else ret = HRTIMER_NORESTART; unlock(&x->lock); and the timer callback returns HRTIMER_RESTART for an armed timer. This is wrong and we run into the BUG_ON() in __run_hrtimer(). This can happens on SMP or PREEMPT-RT. The patch fixes the problem by only starting the timer if the timer is not yet queued. Reported-by: Torben Hohn <torbenh@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> [bigeasy: collected information and created a patch + description based on it] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Felipe Balbi <balbi@ti.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
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