ARM: 6975/1: pmu: reject duplicate PMU registrations

Currently, the PMU reservation framework allows for multiple PMUs of
the same type to register themselves. This can lead to a bug with the
sequence:

register_pmu(pmu1);
reserve_pmu(pmu_type);
register_pmu(pmu2);
release_pmu(pmu1);

Here, pmu1 cannot be released, and pmu2 cannot be reserved.

This patch modifies register_pmu to reject registrations where a PMU is
already present, preventing this problem. PMUs which can have multiple
instances should not use the PMU reservation framework.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/kernel/pmu.c b/arch/arm/kernel/pmu.c
index 87942b9..de6b1b0 100644 (file)
--- a/arch/arm/kernel/pmu.c
+++ b/arch/arm/kernel/pmu.c
@@ -34,13 +34,13 @@ static int __devinit pmu_register(struct platform_device *pdev,
                return -EINVAL;
        }
 
-       if (pmu_devices[type])
-               pr_warning("registering new PMU device type %d overwrites "
-                               "previous registration!\n", type);
-       else
-               pr_info("registered new PMU device of type %d\n",
-                               type);
+       if (pmu_devices[type]) {
+               pr_warning("rejecting duplicate registration of PMU device "
+                       "type %d.", type);
+               return -ENOSPC;
+       }
 
+       pr_info("registered new PMU device of type %d\n", type);
        pmu_devices[type] = pdev;
        return 0;
 }