Patch "ptp: vclock: use mutex to fix "sleep on atomic" bug" has been added to the 6.2-stable tree

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This is a note to let you know that I've just added the patch titled

    ptp: vclock: use mutex to fix "sleep on atomic" bug

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ptp-vclock-use-mutex-to-fix-sleep-on-atomic-bug.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 725bc298f797c73a07ea480f3185dad761580b8b
Author: Íñigo Huguet <ihuguet@xxxxxxxxxx>
Date:   Tue Feb 21 14:06:16 2023 +0100

    ptp: vclock: use mutex to fix "sleep on atomic" bug
    
    [ Upstream commit 67d93ffc0f3c47094750bde6d62e7c5765dc47a6 ]
    
    vclocks were using spinlocks to protect access to its timecounter and
    cyclecounter. Access to timecounter/cyclecounter is backed by the same
    driver callbacks that are used for non-virtual PHCs, but the usage of
    the spinlock imposes a new limitation that didn't exist previously: now
    they're called in atomic context so they mustn't sleep.
    
    Some drivers like sfc or ice may sleep on these callbacks, causing
    errors like "BUG: scheduling while atomic: ptp5/25223/0x00000002"
    
    Fix it replacing the vclock's spinlock by a mutex. It fix the mentioned
    bug and it doesn't introduce longer delays.
    
    I've tested synchronizing various different combinations of clocks:
    - vclock->sysclock
    - sysclock->vclock
    - vclock->vclock
    - hardware PHC in different NIC -> vclock
    - created 4 vclocks and launch 4 parallel phc2sys processes with
      lockdep enabled
    
    In all cases, comparing the delays reported by phc2sys, they are in the
    same range of values than before applying the patch.
    
    Link: https://lore.kernel.org/netdev/69d0ff33-bd32-6aa5-d36c-fbdc3c01337c@xxxxxxxxxx/
    Fixes: 5d43f951b1ac ("ptp: add ptp virtual clock driver framework")
    Reported-by: Yalin Li <yalli@xxxxxxxxxx>
    Suggested-by: Richard Cochran <richardcochran@xxxxxxxxx>
    Tested-by: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
    Signed-off-by: Íñigo Huguet <ihuguet@xxxxxxxxxx>
    Acked-by: Richard Cochran <richardcochran@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20230221130616.21837-1-ihuguet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
index 77918a2c67018..75f58fc468a71 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h
@@ -66,7 +66,7 @@ struct ptp_vclock {
 	struct hlist_node vclock_hash_node;
 	struct cyclecounter cc;
 	struct timecounter tc;
-	spinlock_t lock;	/* protects tc/cc */
+	struct mutex lock;	/* protects tc/cc */
 };
 
 /*
diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c
index 1c0ed4805c0aa..dcf752c9e0450 100644
--- a/drivers/ptp/ptp_vclock.c
+++ b/drivers/ptp/ptp_vclock.c
@@ -43,16 +43,16 @@ static void ptp_vclock_hash_del(struct ptp_vclock *vclock)
 static int ptp_vclock_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 {
 	struct ptp_vclock *vclock = info_to_vclock(ptp);
-	unsigned long flags;
 	s64 adj;
 
 	adj = (s64)scaled_ppm << PTP_VCLOCK_FADJ_SHIFT;
 	adj = div_s64(adj, PTP_VCLOCK_FADJ_DENOMINATOR);
 
-	spin_lock_irqsave(&vclock->lock, flags);
+	if (mutex_lock_interruptible(&vclock->lock))
+		return -EINTR;
 	timecounter_read(&vclock->tc);
 	vclock->cc.mult = PTP_VCLOCK_CC_MULT + adj;
-	spin_unlock_irqrestore(&vclock->lock, flags);
+	mutex_unlock(&vclock->lock);
 
 	return 0;
 }
@@ -60,11 +60,11 @@ static int ptp_vclock_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 static int ptp_vclock_adjtime(struct ptp_clock_info *ptp, s64 delta)
 {
 	struct ptp_vclock *vclock = info_to_vclock(ptp);
-	unsigned long flags;
 
-	spin_lock_irqsave(&vclock->lock, flags);
+	if (mutex_lock_interruptible(&vclock->lock))
+		return -EINTR;
 	timecounter_adjtime(&vclock->tc, delta);
-	spin_unlock_irqrestore(&vclock->lock, flags);
+	mutex_unlock(&vclock->lock);
 
 	return 0;
 }
@@ -73,12 +73,12 @@ static int ptp_vclock_gettime(struct ptp_clock_info *ptp,
 			      struct timespec64 *ts)
 {
 	struct ptp_vclock *vclock = info_to_vclock(ptp);
-	unsigned long flags;
 	u64 ns;
 
-	spin_lock_irqsave(&vclock->lock, flags);
+	if (mutex_lock_interruptible(&vclock->lock))
+		return -EINTR;
 	ns = timecounter_read(&vclock->tc);
-	spin_unlock_irqrestore(&vclock->lock, flags);
+	mutex_unlock(&vclock->lock);
 	*ts = ns_to_timespec64(ns);
 
 	return 0;
@@ -91,7 +91,6 @@ static int ptp_vclock_gettimex(struct ptp_clock_info *ptp,
 	struct ptp_vclock *vclock = info_to_vclock(ptp);
 	struct ptp_clock *pptp = vclock->pclock;
 	struct timespec64 pts;
-	unsigned long flags;
 	int err;
 	u64 ns;
 
@@ -99,9 +98,10 @@ static int ptp_vclock_gettimex(struct ptp_clock_info *ptp,
 	if (err)
 		return err;
 
-	spin_lock_irqsave(&vclock->lock, flags);
+	if (mutex_lock_interruptible(&vclock->lock))
+		return -EINTR;
 	ns = timecounter_cyc2time(&vclock->tc, timespec64_to_ns(&pts));
-	spin_unlock_irqrestore(&vclock->lock, flags);
+	mutex_unlock(&vclock->lock);
 
 	*ts = ns_to_timespec64(ns);
 
@@ -113,11 +113,11 @@ static int ptp_vclock_settime(struct ptp_clock_info *ptp,
 {
 	struct ptp_vclock *vclock = info_to_vclock(ptp);
 	u64 ns = timespec64_to_ns(ts);
-	unsigned long flags;
 
-	spin_lock_irqsave(&vclock->lock, flags);
+	if (mutex_lock_interruptible(&vclock->lock))
+		return -EINTR;
 	timecounter_init(&vclock->tc, &vclock->cc, ns);
-	spin_unlock_irqrestore(&vclock->lock, flags);
+	mutex_unlock(&vclock->lock);
 
 	return 0;
 }
@@ -127,7 +127,6 @@ static int ptp_vclock_getcrosststamp(struct ptp_clock_info *ptp,
 {
 	struct ptp_vclock *vclock = info_to_vclock(ptp);
 	struct ptp_clock *pptp = vclock->pclock;
-	unsigned long flags;
 	int err;
 	u64 ns;
 
@@ -135,9 +134,10 @@ static int ptp_vclock_getcrosststamp(struct ptp_clock_info *ptp,
 	if (err)
 		return err;
 
-	spin_lock_irqsave(&vclock->lock, flags);
+	if (mutex_lock_interruptible(&vclock->lock))
+		return -EINTR;
 	ns = timecounter_cyc2time(&vclock->tc, ktime_to_ns(xtstamp->device));
-	spin_unlock_irqrestore(&vclock->lock, flags);
+	mutex_unlock(&vclock->lock);
 
 	xtstamp->device = ns_to_ktime(ns);
 
@@ -205,7 +205,7 @@ struct ptp_vclock *ptp_vclock_register(struct ptp_clock *pclock)
 
 	INIT_HLIST_NODE(&vclock->vclock_hash_node);
 
-	spin_lock_init(&vclock->lock);
+	mutex_init(&vclock->lock);
 
 	vclock->clock = ptp_clock_register(&vclock->info, &pclock->dev);
 	if (IS_ERR_OR_NULL(vclock->clock)) {
@@ -269,7 +269,6 @@ ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp, int vclock_index)
 {
 	unsigned int hash = vclock_index % HASH_SIZE(vclock_hash);
 	struct ptp_vclock *vclock;
-	unsigned long flags;
 	u64 ns;
 	u64 vclock_ns = 0;
 
@@ -281,9 +280,10 @@ ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp, int vclock_index)
 		if (vclock->clock->index != vclock_index)
 			continue;
 
-		spin_lock_irqsave(&vclock->lock, flags);
+		if (mutex_lock_interruptible(&vclock->lock))
+			break;
 		vclock_ns = timecounter_cyc2time(&vclock->tc, ns);
-		spin_unlock_irqrestore(&vclock->lock, flags);
+		mutex_unlock(&vclock->lock);
 		break;
 	}
 



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