Re: [PATCH v2 1/9] mailbox: imx: Add a channel shutdown field

[Peng Fan <peng.fan@oss.nxp.com>]

On Wed, Jun 03, 2026 at 03:05:04PM +0200, Sebastian Andrzej Siewior wrote:
>sashiko complained about possible teardown problem. The scenario
>
> CPU 0                              CPU 1
>  imx_mu_isr()                   imx_mu_shutdown()
>                                   imx_mu_xcr_rmw(priv, IMX_MU_RCR, 0, IMX_MU_xCR_RIEn(priv->dcfg->type, cp->idx));
>    imx_mu_specific_rx()
>      imx_mu_xcr_rmw(priv, IMX_MU_RCR, IMX_MU_xCR_RIEn(priv->dcfg->type, 0), 0);
>                                   free_irq()
>
>The RX event remains enabled because in this short window the RX event
>was disabled in ->shutdown() while the interrupt was active and then
>enabled again by the ISR while ->shutdown waited in free_irq().
>
>This race requires timing and if happens can be problematic on shared
>handlers if the "removed" channel triggers an interrupt. In this case
>the irq-core will shutdown the interrupt with the "nobody cared"
>message.
>
>Introduce imx_mu_con_priv::shutdown to signal that the channel is
>shutting down. This flag is set with the lock held (by
>imx_mu_xcr_clr_shut()). The unmask side uses imx_mu_xcr_set_act() which
>only enables the event if the channel has not been shutdown and
>serialises on the same lock.
>
>Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Peng Fan <peng.fan@nxp.com>