Commit-ID: a6f089e95b1e08cdea9633d50ad20aa5d44ba64d Gitweb: http://git.kernel.org/tip/a6f089e95b1e08cdea9633d50ad20aa5d44ba64d Author: Lior Amsalem <alior@xxxxxxxxxxx> AuthorDate: Mon, 25 Nov 2013 17:26:44 +0100 Committer: Jason Cooper <jason@xxxxxxxxxxxxxx> CommitDate: Fri, 13 Dec 2013 16:34:04 +0000 irqchip: armada-370-xp: fix IPI race condition 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> Cc: stable@xxxxxxxxxxxxxxx # v3.8+ Fixes: 344e873e5657e8dc0 'arm: mvebu: Add IPI support via doorbells' Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Jason Cooper <jason@xxxxxxxxxxxxxx> --- drivers/irqchip/irq-armada-370-xp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/irqchip/irq-armada-370-xp.c b/drivers/irqchip/irq-armada-370-xp.c index 433cc85..f5e49a2 100644 --- a/drivers/irqchip/irq-armada-370-xp.c +++ b/drivers/irqchip/irq-armada-370-xp.c @@ -407,7 +407,7 @@ armada_370_xp_handle_irq(struct pt_regs *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 linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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