Disabling preemption in the GRU driver is unnecessary, and clashes with
sleeping locks in several code paths.  Remove preempt_disable and
preempt_enable from the GRU driver.

Signed-off-by: Dimitri Sivanich <sivanich@hpe.com>
---
 drivers/misc/sgi-gru/grukservices.c | 2 --
 drivers/misc/sgi-gru/grumain.c      | 4 ----
 drivers/misc/sgi-gru/grutlbpurge.c  | 2 --
 3 files changed, 8 deletions(-)

diff --git a/drivers/misc/sgi-gru/grukservices.c b/drivers/misc/sgi-gru/grukservices.c
index 37e804bbb1f2..205945ce9e86 100644
--- a/drivers/misc/sgi-gru/grukservices.c
+++ b/drivers/misc/sgi-gru/grukservices.c
@@ -258,7 +258,6 @@ static int gru_get_cpu_resources(int dsr_bytes, void **cb, void **dsr)
 	int lcpu;
 
 	BUG_ON(dsr_bytes > GRU_NUM_KERNEL_DSR_BYTES);
-	preempt_disable();
 	bs = gru_lock_kernel_context(-1);
 	lcpu = uv_blade_processor_id();
 	*cb = bs->kernel_cb + lcpu * GRU_HANDLE_STRIDE;
@@ -272,7 +271,6 @@ static int gru_get_cpu_resources(int dsr_bytes, void **cb, void **dsr)
 static void gru_free_cpu_resources(void *cb, void *dsr)
 {
 	gru_unlock_kernel_context(uv_numa_blade_id());
-	preempt_enable();
 }
 
 /*
diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index 0f5b09e290c8..3036c15f3689 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -937,10 +937,8 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
 
 again:
 	mutex_lock(&gts->ts_ctxlock);
-	preempt_disable();
 
 	if (gru_check_context_placement(gts)) {
-		preempt_enable();
 		mutex_unlock(&gts->ts_ctxlock);
 		gru_unload_context(gts, 1);
 		return VM_FAULT_NOPAGE;
@@ -949,7 +947,6 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
 	if (!gts->ts_gru) {
 		STAT(load_user_context);
 		if (!gru_assign_gru_context(gts)) {
-			preempt_enable();
 			mutex_unlock(&gts->ts_ctxlock);
 			set_current_state(TASK_INTERRUPTIBLE);
 			schedule_timeout(GRU_ASSIGN_DELAY);  /* true hack ZZZ */
@@ -965,7 +962,6 @@ vm_fault_t gru_fault(struct vm_fault *vmf)
 				vma->vm_page_prot);
 	}
 
-	preempt_enable();
 	mutex_unlock(&gts->ts_ctxlock);
 
 	return VM_FAULT_NOPAGE;
diff --git a/drivers/misc/sgi-gru/grutlbpurge.c b/drivers/misc/sgi-gru/grutlbpurge.c
index 10921cd2608d..1107dd3e2e9f 100644
--- a/drivers/misc/sgi-gru/grutlbpurge.c
+++ b/drivers/misc/sgi-gru/grutlbpurge.c
@@ -65,7 +65,6 @@ static struct gru_tlb_global_handle *get_lock_tgh_handle(struct gru_state
 	struct gru_tlb_global_handle *tgh;
 	int n;
 
-	preempt_disable();
 	if (uv_numa_blade_id() == gru->gs_blade_id)
 		n = get_on_blade_tgh(gru);
 	else
@@ -79,7 +78,6 @@ static struct gru_tlb_global_handle *get_lock_tgh_handle(struct gru_state
 static void get_unlock_tgh_handle(struct gru_tlb_global_handle *tgh)
 {
 	unlock_tgh_handle(tgh);
-	preempt_enable();
 }
 
 /*
-- 
2.35.3

On Thu, 19 Sept 2024 at 06:16, Dimitri Sivanich <sivanich@hpe.com> wrote:
>
> Disabling preemption in the GRU driver is unnecessary, and clashes with
> sleeping locks in several code paths.  Remove preempt_disable and
> preempt_enable from the GRU driver.

I've applied this directly, since it didn't come in through any of the
normal channels, and I don't see it pending anywhere in linux-next
either.

I doubt it matters much in practice, but at least it should make
smatch happier about this driver, and clearly the preemption disabling
was always wrong.

              Linus

On Wed, Oct 09, 2024 at 12:49:23PM -0700, Linus Torvalds wrote:
> On Thu, 19 Sept 2024 at 06:16, Dimitri Sivanich <sivanich@hpe.com> wrote:
> >
> > Disabling preemption in the GRU driver is unnecessary, and clashes with
> > sleeping locks in several code paths.  Remove preempt_disable and
> > preempt_enable from the GRU driver.
> 
> I've applied this directly, since it didn't come in through any of the
> normal channels, and I don't see it pending anywhere in linux-next
> either.

No problem, I hadn't gotten to it yet in my large patch queue, thanks
for picking it up.

greg k-h