Commit 0590c94c3596 ("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: Adrián Larumbe adrian.larumbe@collabora.com Fixes: 0590c94c3596 ("drm/panthor: Fix race condition when gathering fdinfo group samples") Reviewed-by: Liviu Dudau liviu.dudau@arm.com Reviewed-by: Boris Brezillon boris.brezillon@collabora.com Reviewed-by: Steven Price steven.price@arm.com Signed-off-by: Steven Price steven.price@arm.com Link: https://patchwork.freedesktop.org/patch/msgid/20250303190923.1639985-1-adria... (cherry picked from commit e379856b428acafb8ed689f31d65814da6447b2e) --- drivers/gpu/drm/panthor/panthor_sched.c | 28 ++++++++++++------------- 1 file changed, 13 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c index eb2c2ca375d7..52b5543acc19 100644 --- a/drivers/gpu/drm/panthor/panthor_sched.c +++ b/drivers/gpu/drm/panthor/panthor_sched.c @@ -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> @@ -620,14 +621,14 @@ struct panthor_group {
/** @fdinfo: Per-file total cycle and timestamp values reference. */ struct { - /** @data: Total sampled values for jobs in queues from this group. */ + /** @fdinfo.data: Total sampled values for jobs in queues from this 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;
/** @state: Group state. */ @@ -900,8 +901,6 @@ 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]);
@@ -2845,12 +2844,12 @@ 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); - 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); + 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; + } }
void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile) @@ -2864,12 +2863,11 @@ 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); } @@ -3491,7 +3489,7 @@ int panthor_group_create(struct panthor_file *pfile, } mutex_unlock(&sched->reset.lock);
- mutex_init(&group->fdinfo.lock); + spin_lock_init(&group->fdinfo.lock);
return gid;