Commit 0b167f11 authored Oct 19, 2017 by Guilherme G. Piccoli Committed by Michael Ellerman Oct 25, 2017

powerpc/perf: Fix IMC allocation routine

When setting nr_cpus=1, we observed a crash in IMC code during boot
due to a missing allocation: basically, IMC code is taking the number
of threads into account in imc_mem_init() and if we manually set
nr_cpus for a value that is not multiple of the number of threads per
core, an integer division in that function will discard the decimal
portion, leading IMC to not allocate one mem_info struct. This causes
a NULL pointer dereference later, on is_core_imc_mem_inited().

This patch just rounds that division up, fixing the bug.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Acked-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent 0d8ba162

arch/powerpc/perf/imc-pmu.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1104,7 +1104,7 @@ static int init_nest_pmu_ref(void)

		static void cleanup_all_core_imc_memory(void)
		{
		int i, nr_cores = num_present_cpus() / threads_per_core;
		int i, nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core);
		struct imc_mem_info *ptr = core_imc_pmu->mem_info;
		int size = core_imc_pmu->counter_mem_size;

		@@ -1212,7 +1212,7 @@ static int imc_mem_init(struct imc_pmu pmu_ptr, struct device_node parent,
		if (!pmu_ptr->pmu.name)
		return -ENOMEM;

		nr_cores = num_present_cpus() / threads_per_core;
		nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core);
		pmu_ptr->mem_info = kcalloc(nr_cores, sizeof(struct imc_mem_info),
		GFP_KERNEL);