| Message ID | 20250210124203.124191-1-adrian.larumbe@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] drm/panthor: Replace sleep locks with spinlocks in fdinfo path | expand |
On Mon, 10 Feb 2025 12:41:59 +0000 Adrián Larumbe <adrian.larumbe@collabora.com> wrote: > Panthor's fdinfo handler is routed through the /proc file system, which > executes in an atomic context. That means we cannot use mutexes because > they might sleep. > > This bug was uncovered by enabling some of the kernel's mutex-debugging > features: > > 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> > --- > drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- > 1 file changed, 12 insertions(+), 14 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 0b93bf83a9b2..7a267d1efeb6 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> > @@ -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); > - 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) > @@ -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); > } > @@ -3531,7 +3529,7 @@ 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; > > > base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa > prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa > prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 > prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 > prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 > prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5
On Mon, Feb 10, 2025 at 12:41:59PM +0000, Adrián Larumbe wrote: > Panthor's fdinfo handler is routed through the /proc file system, which > executes in an atomic context. That means we cannot use mutexes because > they might sleep. > > This bug was uncovered by enabling some of the kernel's mutex-debugging > features: > > 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") Reviewed-by: Liviu Dudau <liviu.dudau@arm.com> Best regards, Liviu > --- > drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- > 1 file changed, 12 insertions(+), 14 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 0b93bf83a9b2..7a267d1efeb6 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> > @@ -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); > - 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) > @@ -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); > } > @@ -3531,7 +3529,7 @@ 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; > > > base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa > prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa > prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 > prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 > prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 > prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5 > -- > 2.47.1 >
On 10/02/2025 12:41, Adrián Larumbe wrote: > Panthor's fdinfo handler is routed through the /proc file system, which > executes in an atomic context. That means we cannot use mutexes because > they might sleep. Have the debug splat at hand? I am thinking it is not because of fdinfo reads, which are allowed to sleep, but has to be something else. Regards, Tvrtko > This bug was uncovered by enabling some of the kernel's mutex-debugging > features: > > 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") > --- > drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- > 1 file changed, 12 insertions(+), 14 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 0b93bf83a9b2..7a267d1efeb6 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> > @@ -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); > - 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) > @@ -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); > } > @@ -3531,7 +3529,7 @@ 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; > > > base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa > prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa > prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 > prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 > prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 > prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5
Hi Tvrtko, [18153.770244] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 [18153.771059] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203412, name: cat [18153.771757] preempt_count: 1, expected: 0 [18153.772164] RCU nest depth: 0, expected: 0 [18153.772538] INFO: lockdep is turned off. [18153.772898] CPU: 4 UID: 0 PID: 203412 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 [18153.772906] Tainted: [W]=WARN [18153.772908] Hardware name: Radxa ROCK 5B (DT) [18153.772911] Call trace: [18153.772913] show_stack+0x24/0x38 (C) [18153.772927] dump_stack_lvl+0x3c/0x98 [18153.772935] dump_stack+0x18/0x24 [18153.772941] __might_resched+0x298/0x2b0 [18153.772948] __might_sleep+0x6c/0xb0 [18153.772953] __mutex_lock_common+0x7c/0x1950 [18153.772962] mutex_lock_nested+0x38/0x50 [18153.772969] panthor_fdinfo_gather_group_samples+0x80/0x138 [panthor] [18153.773042] panthor_show_fdinfo+0x80/0x228 [panthor] [18153.773109] drm_show_fdinfo+0x1a4/0x1e0 [drm] [18153.773397] seq_show+0x274/0x358 [18153.773404] seq_read_iter+0x1d4/0x630 [18153.773411] seq_read+0x148/0x1a0 [18153.773416] vfs_read+0x114/0x3e0 [18153.773423] ksys_read+0x90/0x110 [18153.773429] __arm64_sys_read+0x50/0x70 [18153.773435] invoke_syscall+0x60/0x178 [18153.773442] el0_svc_common+0x104/0x148 [18153.773447] do_el0_svc+0x3c/0x58 [18153.773453] el0_svc+0x50/0xa8 [18153.773459] el0t_64_sync_handler+0x78/0x108 [18153.773465] el0t_64_sync+0x198/0x1a0 On 10.02.2025 15:52, Tvrtko Ursulin wrote: > On 10/02/2025 12:41, Adrián Larumbe wrote: > > Panthor's fdinfo handler is routed through the /proc file system, which > > executes in an atomic context. That means we cannot use mutexes because > > they might sleep. > > Have the debug splat at hand? I am thinking it is not because of fdinfo reads, > which are allowed to sleep, but has to be something else. > > Regards, > > Tvrtko > > > This bug was uncovered by enabling some of the kernel's mutex-debugging > > features: > > > > 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") > > --- > > drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- > > 1 file changed, 12 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > > index 0b93bf83a9b2..7a267d1efeb6 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> > > @@ -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); > > - 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) > > @@ -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); > > } > > @@ -3531,7 +3529,7 @@ 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; > > > > base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa > > prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa > > prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 > > prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 > > prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 > > prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5
This is the debug log for the second patch in the series: [18325.029172] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 [18325.029947] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203483, name: cat [18325.030646] preempt_count: 1, expected: 0 [18325.031012] RCU nest depth: 0, expected: 0 [18325.031387] INFO: lockdep is turned off. [18325.031754] CPU: 4 UID: 0 PID: 203483 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 [18325.031763] Tainted: [W]=WARN [18325.031767] Hardware name: Radxa ROCK 5B (DT) [18325.031772] Call trace: [18325.031777] show_stack+0x24/0x38 (C) [18325.031813] dump_stack_lvl+0x3c/0x98 [18325.031827] dump_stack+0x18/0x24 [18325.031833] __might_resched+0x298/0x2b0 [18325.031844] __might_sleep+0x6c/0xb0 [18325.031850] __mutex_lock_common+0x7c/0x1950 [18325.031875] mutex_lock_nested+0x38/0x50 [18325.031889] panthor_vm_heaps_sizes+0xa8/0x158 [panthor] [18325.031973] panthor_show_fdinfo+0x1a0/0x228 [panthor] [18325.032040] drm_show_fdinfo+0x1a4/0x1e0 [drm] [18325.032328] seq_show+0x274/0x358 [18325.032343] seq_read_iter+0x1d4/0x630 [18325.032358] seq_read+0x148/0x1a0 [18325.032364] vfs_read+0x114/0x3e0 [18325.032377] ksys_read+0x90/0x110 [18325.032383] __arm64_sys_read+0x50/0x70 [18325.032389] invoke_syscall+0x60/0x178 [18325.032400] el0_svc_common+0x104/0x148 [18325.032406] do_el0_svc+0x3c/0x58 [18325.032413] el0_svc+0x50/0xa8 [18325.032422] el0t_64_sync_handler+0x78/0x108 [18325.032427] el0t_64_sync+0x198/0x1a0 On 10.02.2025 15:52, Tvrtko Ursulin wrote: > > On 10/02/2025 12:41, Adrián Larumbe wrote: > > Panthor's fdinfo handler is routed through the /proc file system, which > > executes in an atomic context. That means we cannot use mutexes because > > they might sleep. > > Have the debug splat at hand? I am thinking it is not because of fdinfo reads, > which are allowed to sleep, but has to be something else. > > Regards, > > Tvrtko > > > This bug was uncovered by enabling some of the kernel's mutex-debugging > > features: > > > > 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") > > --- > > drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- > > 1 file changed, 12 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > > index 0b93bf83a9b2..7a267d1efeb6 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> > > @@ -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); > > - 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) > > @@ -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); > > } > > @@ -3531,7 +3529,7 @@ 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; > > > > base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa > > prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa > > prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 > > prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 > > prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 > > prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5
On 10/02/2025 16:08, Adrián Larumbe wrote: > Hi Tvrtko, Thanks! > [18153.770244] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 > [18153.771059] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203412, name: cat > [18153.771757] preempt_count: 1, expected: 0 > [18153.772164] RCU nest depth: 0, expected: 0 > [18153.772538] INFO: lockdep is turned off. > [18153.772898] CPU: 4 UID: 0 PID: 203412 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 > [18153.772906] Tainted: [W]=WARN > [18153.772908] Hardware name: Radxa ROCK 5B (DT) > [18153.772911] Call trace: > [18153.772913] show_stack+0x24/0x38 (C) > [18153.772927] dump_stack_lvl+0x3c/0x98 > [18153.772935] dump_stack+0x18/0x24 > [18153.772941] __might_resched+0x298/0x2b0 > [18153.772948] __might_sleep+0x6c/0xb0 > [18153.772953] __mutex_lock_common+0x7c/0x1950 > [18153.772962] mutex_lock_nested+0x38/0x50 > [18153.772969] panthor_fdinfo_gather_group_samples+0x80/0x138 [panthor] > [18153.773042] panthor_show_fdinfo+0x80/0x228 [panthor] > [18153.773109] drm_show_fdinfo+0x1a4/0x1e0 [drm] > [18153.773397] seq_show+0x274/0x358 > [18153.773404] seq_read_iter+0x1d4/0x630 There is a mutex_lock literally in seq_read_iter. So colour me confused. What created the atomic context between then and Panthor code?! I just don't see it. Regards, Tvrtko > [18153.773411] seq_read+0x148/0x1a0 > [18153.773416] vfs_read+0x114/0x3e0 > [18153.773423] ksys_read+0x90/0x110 > [18153.773429] __arm64_sys_read+0x50/0x70 > [18153.773435] invoke_syscall+0x60/0x178 > [18153.773442] el0_svc_common+0x104/0x148 > [18153.773447] do_el0_svc+0x3c/0x58 > [18153.773453] el0_svc+0x50/0xa8 > [18153.773459] el0t_64_sync_handler+0x78/0x108 > [18153.773465] el0t_64_sync+0x198/0x1a0 > > > On 10.02.2025 15:52, Tvrtko Ursulin wrote: >> On 10/02/2025 12:41, Adrián Larumbe wrote: >>> Panthor's fdinfo handler is routed through the /proc file system, which >>> executes in an atomic context. That means we cannot use mutexes because >>> they might sleep. >> >> Have the debug splat at hand? I am thinking it is not because of fdinfo reads, >> which are allowed to sleep, but has to be something else. >> >> Regards, >> >> Tvrtko >> >>> This bug was uncovered by enabling some of the kernel's mutex-debugging >>> features: >>> >>> 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") >>> --- >>> drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- >>> 1 file changed, 12 insertions(+), 14 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c >>> index 0b93bf83a9b2..7a267d1efeb6 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> >>> @@ -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); >>> - 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) >>> @@ -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); >>> } >>> @@ -3531,7 +3529,7 @@ 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; >>> >>> base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa >>> prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa >>> prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 >>> prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 >>> prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 >>> prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5
On Tue, 11 Feb 2025 11:39:49 +0000 Tvrtko Ursulin <tursulin@ursulin.net> wrote: > On 10/02/2025 16:08, Adrián Larumbe wrote: > > Hi Tvrtko, > > Thanks! > > > [18153.770244] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 > > [18153.771059] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203412, name: cat > > [18153.771757] preempt_count: 1, expected: 0 > > [18153.772164] RCU nest depth: 0, expected: 0 > > [18153.772538] INFO: lockdep is turned off. > > [18153.772898] CPU: 4 UID: 0 PID: 203412 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 > > [18153.772906] Tainted: [W]=WARN > > [18153.772908] Hardware name: Radxa ROCK 5B (DT) > > [18153.772911] Call trace: > > [18153.772913] show_stack+0x24/0x38 (C) > > [18153.772927] dump_stack_lvl+0x3c/0x98 > > [18153.772935] dump_stack+0x18/0x24 > > [18153.772941] __might_resched+0x298/0x2b0 > > [18153.772948] __might_sleep+0x6c/0xb0 > > [18153.772953] __mutex_lock_common+0x7c/0x1950 > > [18153.772962] mutex_lock_nested+0x38/0x50 > > [18153.772969] panthor_fdinfo_gather_group_samples+0x80/0x138 [panthor] > > [18153.773042] panthor_show_fdinfo+0x80/0x228 [panthor] > > [18153.773109] drm_show_fdinfo+0x1a4/0x1e0 [drm] > > [18153.773397] seq_show+0x274/0x358 > > [18153.773404] seq_read_iter+0x1d4/0x630 > > There is a mutex_lock literally in seq_read_iter. > > So colour me confused. What created the atomic context between then and > Panthor code?! I just don't see it. Uh, looks like we've leaked an atomic context somewhere, indeed. Adrian, do you have a reliable reproducer for this bug?
Hi Boris, Here are the branch and kernel config I used for reproducing the bug: https://gitlab.freedesktop.org/larumbe/drm-misc/-/tree/panthor-fdinfo-internalbosizes-10 https://gitlab.collabora.com/-/snippets/426 On 11.02.2025 13:41, Boris Brezillon wrote: > On Tue, 11 Feb 2025 11:39:49 +0000 > Tvrtko Ursulin <tursulin@ursulin.net> wrote: > > > On 10/02/2025 16:08, Adrián Larumbe wrote: > > > Hi Tvrtko, > > > > Thanks! > > > > > [18153.770244] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 > > > [18153.771059] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203412, name: cat > > > [18153.771757] preempt_count: 1, expected: 0 > > > [18153.772164] RCU nest depth: 0, expected: 0 > > > [18153.772538] INFO: lockdep is turned off. > > > [18153.772898] CPU: 4 UID: 0 PID: 203412 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 > > > [18153.772906] Tainted: [W]=WARN > > > [18153.772908] Hardware name: Radxa ROCK 5B (DT) > > > [18153.772911] Call trace: > > > [18153.772913] show_stack+0x24/0x38 (C) > > > [18153.772927] dump_stack_lvl+0x3c/0x98 > > > [18153.772935] dump_stack+0x18/0x24 > > > [18153.772941] __might_resched+0x298/0x2b0 > > > [18153.772948] __might_sleep+0x6c/0xb0 > > > [18153.772953] __mutex_lock_common+0x7c/0x1950 > > > [18153.772962] mutex_lock_nested+0x38/0x50 > > > [18153.772969] panthor_fdinfo_gather_group_samples+0x80/0x138 [panthor] > > > [18153.773042] panthor_show_fdinfo+0x80/0x228 [panthor] > > > [18153.773109] drm_show_fdinfo+0x1a4/0x1e0 [drm] > > > [18153.773397] seq_show+0x274/0x358 > > > [18153.773404] seq_read_iter+0x1d4/0x630 > > > > There is a mutex_lock literally in seq_read_iter. > > > > So colour me confused. What created the atomic context between then and > > Panthor code?! I just don't see it. > > Uh, looks like we've leaked an atomic context somewhere, indeed. > Adrian, do you have a reliable reproducer for this bug? Adrian Larumbe
On Tue, 11 Feb 2025 11:39:49 +0000 Tvrtko Ursulin <tursulin@ursulin.net> wrote: > On 10/02/2025 16:08, Adrián Larumbe wrote: > > Hi Tvrtko, > > Thanks! > > > [18153.770244] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 > > [18153.771059] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203412, name: cat > > [18153.771757] preempt_count: 1, expected: 0 > > [18153.772164] RCU nest depth: 0, expected: 0 > > [18153.772538] INFO: lockdep is turned off. > > [18153.772898] CPU: 4 UID: 0 PID: 203412 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 > > [18153.772906] Tainted: [W]=WARN > > [18153.772908] Hardware name: Radxa ROCK 5B (DT) > > [18153.772911] Call trace: > > [18153.772913] show_stack+0x24/0x38 (C) > > [18153.772927] dump_stack_lvl+0x3c/0x98 > > [18153.772935] dump_stack+0x18/0x24 > > [18153.772941] __might_resched+0x298/0x2b0 > > [18153.772948] __might_sleep+0x6c/0xb0 > > [18153.772953] __mutex_lock_common+0x7c/0x1950 > > [18153.772962] mutex_lock_nested+0x38/0x50 > > [18153.772969] panthor_fdinfo_gather_group_samples+0x80/0x138 [panthor] > > [18153.773042] panthor_show_fdinfo+0x80/0x228 [panthor] > > [18153.773109] drm_show_fdinfo+0x1a4/0x1e0 [drm] > > [18153.773397] seq_show+0x274/0x358 > > [18153.773404] seq_read_iter+0x1d4/0x630 > > There is a mutex_lock literally in seq_read_iter. > > So colour me confused. What created the atomic context between then and > Panthor code?! I just don't see it. It's actually the xa_lock() we take when gathering fdinfo data that puts us in this atomic context. In other words, the fix is correct, but the explanation is wrong :-).
On 12/02/2025 16:33, Boris Brezillon wrote: > On Tue, 11 Feb 2025 11:39:49 +0000 > Tvrtko Ursulin <tursulin@ursulin.net> wrote: > >> On 10/02/2025 16:08, Adrián Larumbe wrote: >>> Hi Tvrtko, >> >> Thanks! >> >>> [18153.770244] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:562 >>> [18153.771059] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 203412, name: cat >>> [18153.771757] preempt_count: 1, expected: 0 >>> [18153.772164] RCU nest depth: 0, expected: 0 >>> [18153.772538] INFO: lockdep is turned off. >>> [18153.772898] CPU: 4 UID: 0 PID: 203412 Comm: cat Tainted: G W 6.14.0-rc1-panthor-next-rk3588-fdinfo+ #1 >>> [18153.772906] Tainted: [W]=WARN >>> [18153.772908] Hardware name: Radxa ROCK 5B (DT) >>> [18153.772911] Call trace: >>> [18153.772913] show_stack+0x24/0x38 (C) >>> [18153.772927] dump_stack_lvl+0x3c/0x98 >>> [18153.772935] dump_stack+0x18/0x24 >>> [18153.772941] __might_resched+0x298/0x2b0 >>> [18153.772948] __might_sleep+0x6c/0xb0 >>> [18153.772953] __mutex_lock_common+0x7c/0x1950 >>> [18153.772962] mutex_lock_nested+0x38/0x50 >>> [18153.772969] panthor_fdinfo_gather_group_samples+0x80/0x138 [panthor] >>> [18153.773042] panthor_show_fdinfo+0x80/0x228 [panthor] >>> [18153.773109] drm_show_fdinfo+0x1a4/0x1e0 [drm] >>> [18153.773397] seq_show+0x274/0x358 >>> [18153.773404] seq_read_iter+0x1d4/0x630 >> >> There is a mutex_lock literally in seq_read_iter. >> >> So colour me confused. What created the atomic context between then and >> Panthor code?! I just don't see it. > > It's actually the xa_lock() we take when gathering fdinfo data that > puts us in this atomic context. In other words, the fix is correct, but > the explanation is wrong :-). Huh I did not spot that when glancing over it yesterday or so, but anyway, excellent you figured it out! Now the commit message can be fixed and not mislead someone in the future to think mutexes cannot be used in fdinfo. Thanks for taking time to check it! Regards, Tvrtko
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c index 0b93bf83a9b2..7a267d1efeb6 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> @@ -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); - 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) @@ -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); } @@ -3531,7 +3529,7 @@ 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;
Panthor's fdinfo handler is routed through the /proc file system, which executes in an atomic context. That means we cannot use mutexes because they might sleep. This bug was uncovered by enabling some of the kernel's mutex-debugging features: 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: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") --- drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- 1 file changed, 12 insertions(+), 14 deletions(-) base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5