Commit e379856b authored by Adrián Larumbe's avatar Adrián Larumbe Committed by Steven Price
Browse files

drm/panthor: Replace sleep locks with spinlocks in fdinfo path 



Commit 0590c94c ("drm/panthor: Fix race condition when gathering fdinfo
group samples") introduced an xarray lock to deal with potential
use-after-free errors when accessing groups fdinfo figures. However, this
toggles the kernel's atomic context status, so the next nested mutex lock
will raise a warning when the kernel is compiled with mutex debug options:

CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_MUTEXES=y

Replace Panthor's group fdinfo data mutex with a guarded spinlock.

Signed-off-by: default avatarAdrián Larumbe <adrian.larumbe@collabora.com>
Fixes: 0590c94c ("drm/panthor: Fix race condition when gathering fdinfo group samples")
Reviewed-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
Reviewed-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Signed-off-by: default avatarSteven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250303190923.1639985-1-adrian.larumbe@collabora.com
parent e4c0fd3f

drivers/gpu/drm/panthor/panthor_sched.c

+12 −14
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#include <drm/panthor_drm.h>



#include <linux/build_bug.h>

#include <linux/cleanup.h>

#include <linux/clk.h>

#include <linux/delay.h>

#include <linux/dma-mapping.h>
@@ -631,10 +632,10 @@ struct panthor_group { 
		struct panthor_gpu_usage data;



		/**

		 * @lock: Mutex to govern concurrent access from drm file's fdinfo callback

		 * and job post-completion processing function

		 * @fdinfo.lock: Spinlock to govern concurrent access from drm file's fdinfo

		 * callback and job post-completion processing function

		 */

		struct mutex lock;

		spinlock_t lock;



		/** @fdinfo.kbo_sizes: Aggregate size of private kernel BO's held by the group. */

		size_t kbo_sizes;
@@ -910,8 +911,6 @@ static void group_release_work(struct work_struct *work) 
						   release_work);

	u32 i;



	mutex_destroy(&group->fdinfo.lock);



	for (i = 0; i < group->queue_count; i++)

		group_free_queue(group, group->queues[i]);
@@ -2861,12 +2860,12 @@ static void update_fdinfo_stats(struct panthor_job *job) 
	struct panthor_job_profiling_data *slots = queue->profiling.slots->kmap;

	struct panthor_job_profiling_data *data = &slots[job->profiling.slot];



	mutex_lock(&group->fdinfo.lock);

	scoped_guard(spinlock, &group->fdinfo.lock) {

		if (job->profiling.mask & PANTHOR_DEVICE_PROFILING_CYCLES)

			fdinfo->cycles += data->cycles.after - data->cycles.before;

		if (job->profiling.mask & PANTHOR_DEVICE_PROFILING_TIMESTAMP)

			fdinfo->time += data->time.after - data->time.before;

	mutex_unlock(&group->fdinfo.lock);

	}

}



void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
@@ -2880,12 +2879,11 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile) 


	xa_lock(&gpool->xa);

	xa_for_each(&gpool->xa, i, group) {

		mutex_lock(&group->fdinfo.lock);

		guard(spinlock)(&group->fdinfo.lock);

		pfile->stats.cycles += group->fdinfo.data.cycles;

		pfile->stats.time += group->fdinfo.data.time;

		group->fdinfo.data.cycles = 0;

		group->fdinfo.data.time = 0;

		mutex_unlock(&group->fdinfo.lock);

	}

	xa_unlock(&gpool->xa);

}
@@ -3537,7 +3535,7 @@ int panthor_group_create(struct panthor_file *pfile, 
	mutex_unlock(&sched->reset.lock);



	add_group_kbo_sizes(group->ptdev, group);

	mutex_init(&group->fdinfo.lock);

	spin_lock_init(&group->fdinfo.lock);



	return gid;