Merge "msm: rtb: Fix buffer corruption issue"

/*

 * Copyright (c) 2013-2014, The Linux Foundation. All rights reserved.

 * Copyright (c) 2013-2015, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and

}

#if defined(CONFIG_MSM_RTB_SEPARATE_CPUS)

/*

 * Since it is not necessarily true that nentries % step_size == 0,

 * must make appropriate adjustments to the index when a "wraparound"

 * occurs to ensure that msm_rtb.rtb[x] always belongs to the same cpu.

 * It is desired to give all cpus the same number of entries; this leaves

 * (nentries % step_size) dead space at the end of the buffer.

 */

static int msm_rtb_get_idx(void)

{

	int cpu, i, offset;

	atomic_t *index;

	unsigned long flags;

	u32 unused_buffer_size = msm_rtb.nentries % msm_rtb.step_size;

	int adjusted_size;

	/*

	 * ideally we would use get_cpu but this is a close enough

	index = &per_cpu(msm_rtb_idx_cpu, cpu);

	local_irq_save(flags);

	i = atomic_add_return(msm_rtb.step_size, index);

	i -= msm_rtb.step_size;

	/* Check if index has wrapped around */

	offset = (i & (msm_rtb.nentries - 1)) -

		 ((i - msm_rtb.step_size) & (msm_rtb.nentries - 1));

	/*

	 * Check if index has wrapped around or is in the unused region at the

	 * end of the buffer

	 */

	adjusted_size = atomic_read(index) + unused_buffer_size;

	offset = (adjusted_size & (msm_rtb.nentries - 1)) -

		 ((adjusted_size - msm_rtb.step_size) & (msm_rtb.nentries - 1));

	if (offset < 0) {

		uncached_logk_timestamp(i);

		i = atomic_add_return(msm_rtb.step_size, index);

		i = atomic_add_return(msm_rtb.step_size + unused_buffer_size,

									index);

		i -= msm_rtb.step_size;

	}

	local_irq_restore(flags);

	return i;

}