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Revision 787252a10d9422f3058df9a4821f389e5326c440 authored by Nathan Lynch on 15 October 2021, 17:39:02 UTC, committed by Michael Ellerman on 20 October 2021, 10:38:01 UTC 
powerpc/smp: do not decrement idle task preempt count in CPU offline
 
With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we
get:

BUG: scheduling while atomic: swapper/1/0/0x00000000
no locks held by swapper/1/0.
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100
Call Trace:
 dump_stack_lvl+0xac/0x108
 __schedule_bug+0xac/0xe0
 __schedule+0xcf8/0x10d0
 schedule_idle+0x3c/0x70
 do_idle+0x2d8/0x4a0
 cpu_startup_entry+0x38/0x40
 start_secondary+0x2ec/0x3a0
 start_secondary_prolog+0x10/0x14

This is because powerpc's arch_cpu_idle_dead() decrements the idle task's
preempt count, for reasons explained in commit a7c2bb8279d2 ("powerpc:
Re-enable preemption before cpu_die()"), specifically "start_secondary()
expects a preempt_count() of 0."

However, since commit 2c669ef6979c ("powerpc/preempt: Don't touch the idle
task's preempt_count during hotplug") and commit f1a0a376ca0c ("sched/core:
Initialize the idle task with preemption disabled"), that justification no
longer holds.

The idle task isn't supposed to re-enable preemption, so remove the
vestigial preempt_enable() from the CPU offline path.

Tested with pseries and powernv in qemu, and pseries on PowerVM.

Fixes: 2c669ef6979c ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug")
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211015173902.2278118-1-nathanl@linux.ibm.com
1 parent 496c5fe
Raw File
hda_chmap.h 
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * For multichannel support
 */

#ifndef __SOUND_HDA_CHMAP_H
#define __SOUND_HDA_CHMAP_H

#include <sound/pcm.h>
#include <sound/hdaudio.h>


#define SND_PRINT_CHANNEL_ALLOCATION_ADVISED_BUFSIZE 80

struct hdac_cea_channel_speaker_allocation {
	int ca_index;
	int speakers[8];

	/* derived values, just for convenience */
	int channels;
	int spk_mask;
};
struct hdac_chmap;

struct hdac_chmap_ops {
	/*
	 * Helpers for producing the channel map TLVs. These can be overridden
	 * for devices that have non-standard mapping requirements.
	 */
	int (*chmap_cea_alloc_validate_get_type)(struct hdac_chmap *chmap,
		struct hdac_cea_channel_speaker_allocation *cap, int channels);
	void (*cea_alloc_to_tlv_chmap)(struct hdac_chmap *hchmap,
		struct hdac_cea_channel_speaker_allocation *cap,
		unsigned int *chmap, int channels);

	/* check that the user-given chmap is supported */
	int (*chmap_validate)(struct hdac_chmap *hchmap, int ca,
			int channels, unsigned char *chmap);

	int (*get_spk_alloc)(struct hdac_device *hdac, int pcm_idx);

	void (*get_chmap)(struct hdac_device *hdac, int pcm_idx,
					unsigned char *chmap);
	void (*set_chmap)(struct hdac_device *hdac, int pcm_idx,
			unsigned char *chmap, int prepared);
	bool (*is_pcm_attached)(struct hdac_device *hdac, int pcm_idx);

	/* get and set channel assigned to each HDMI ASP (audio sample packet) slot */
	int (*pin_get_slot_channel)(struct hdac_device *codec,
			hda_nid_t pin_nid, int asp_slot);
	int (*pin_set_slot_channel)(struct hdac_device *codec,
			hda_nid_t pin_nid, int asp_slot, int channel);
	void (*set_channel_count)(struct hdac_device *codec,
				hda_nid_t cvt_nid, int chs);
};

struct hdac_chmap {
	unsigned int channels_max; /* max over all cvts */
	struct hdac_chmap_ops ops;
	struct hdac_device *hdac;
};

void snd_hdac_register_chmap_ops(struct hdac_device *hdac,
				struct hdac_chmap *chmap);
int snd_hdac_channel_allocation(struct hdac_device *hdac, int spk_alloc,
			int channels, bool chmap_set,
			bool non_pcm, unsigned char *map);
int snd_hdac_get_active_channels(int ca);
void snd_hdac_setup_channel_mapping(struct hdac_chmap *chmap,
		       hda_nid_t pin_nid, bool non_pcm, int ca,
		       int channels, unsigned char *map,
		       bool chmap_set);
void snd_hdac_print_channel_allocation(int spk_alloc, char *buf, int buflen);
struct hdac_cea_channel_speaker_allocation *snd_hdac_get_ch_alloc_from_ca(int ca);
int snd_hdac_chmap_to_spk_mask(unsigned char c);
int snd_hdac_spk_to_chmap(int spk);
int snd_hdac_add_chmap_ctls(struct snd_pcm *pcm, int pcm_idx,
				struct hdac_chmap *chmap);
#endif /* __SOUND_HDA_CHMAP_H */
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