3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lior Amsalem <alior@xxxxxxxxxxx> commit a6f089e95b1e08cdea9633d50ad20aa5d44ba64d upstream. In the Armada 370/XP driver, when we receive an IRQ 0, we read the list of doorbells that caused the interrupt from register ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS. This gives the list of IPIs that were generated. However, instead of acknowledging only the IPIs that were generated, we acknowledge *all* the IPIs, by writing ~IPI_DOORBELL_MASK in the ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS register. This creates a race condition: if a new IPI that isn't part of the ones read into the temporary "ipimask" variable is fired before we acknowledge all IPIs, then we will simply loose it. This is causing scheduling hangs on SMP intensive workloads. It is important to mention that this ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS register has the following behavior: "A CPU write of 0 clears the bits in this field. A CPU write of 1 has no effect". This is what allows us to simply write ~ipimask to acknoledge the handled IPIs. Notice that the same problem is present in the MSI implementation, but it will be fixed as a separate patch, so that this IPI fix can be pushed to older stable versions as appropriate (all the way to 3.8), while the MSI code only appeared in 3.13. Signed-off-by: Lior Amsalem <alior@xxxxxxxxxxx> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx> Fixes: 344e873e5657e8dc0 'arm: mvebu: Add IPI support via doorbells' Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Jason Cooper <jason@xxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/irqchip/irq-armada-370-xp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/irqchip/irq-armada-370-xp.c +++ b/drivers/irqchip/irq-armada-370-xp.c @@ -229,7 +229,7 @@ armada_370_xp_handle_irq(struct pt_regs ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS) & IPI_DOORBELL_MASK; - writel(~IPI_DOORBELL_MASK, per_cpu_int_base + + writel(~ipimask, per_cpu_int_base + ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS); /* Handle all pending doorbells */ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html