linux-kernel - [PATCH AUTOSEL 5.15 8/8] misc: sgi-gru: Don't disable preemption in GRU driver

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Message-ID: <20241014035929.2251266-8-sashal@kernel.org>
Date: Sun, 13 Oct 2024 23:59:23 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Dimitri Sivanich <sivanich@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Sasha Levin <sashal@...nel.org>,
	dimitri.sivanich@....com,
	gregkh@...uxfoundation.org
Subject: [PATCH AUTOSEL 5.15 8/8] misc: sgi-gru: Don't disable preemption in GRU driver

From: Dimitri Sivanich <sivanich@....com>

[ Upstream commit b983b271662bd6104d429b0fd97af3333ba760bf ]

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@....com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 0ea923fe6371b..e2bdba4742930 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 3a16eb8e03f73..9b8bdd57ec854 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -941,10 +941,8 @@ 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;
@@ -953,7 +951,6 @@ 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 */
@@ -969,7 +966,6 @@ 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 10921cd2608df..1107dd3e2e9fa 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();
 }
 
 /*
-- 
2.43.0