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Commit 0ad9b204 authored by Eran Ben Elisha's avatar Eran Ben Elisha Committed by David S. Miller
Browse files

net/mlx5e: Fix soft lockup when HW Timestamping is enabled 



Readers/Writers lock for SW timecounter was acquired without disabling
interrupts on local CPU.

The problematic scenario:
* HW timestamping is enabled
* Timestamp overflow periodic service task is running on local CPU and
  holding write_lock for SW timecounter
* Completion arrives, triggers interrupt for local CPU.
  Interrupt routine calls napi_schedule(), which triggers rx/tx
  skb process.
  An attempt to read SW timecounter using read_lock is done, which is
  already locked by a writer on the same CPU and cause soft lockup.

Add irqsave/irqrestore for when using the readers/writers lock for
writing.

Fixes: ef9814de ('net/mlx5e: Add HW timestamping (TS) support')
Signed-off-by: default avatarEran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: default avatarSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ab0394fe

drivers/net/ethernet/mellanox/mlx5/core/en_clock.c

+15 −10
Original line number Diff line number Diff line
@@ -62,10 +62,11 @@ static void mlx5e_timestamp_overflow(struct work_struct *work) 
	struct delayed_work *dwork = to_delayed_work(work);

	struct mlx5e_tstamp *tstamp = container_of(dwork, struct mlx5e_tstamp,

						   overflow_work);

	unsigned long flags;



	write_lock(&tstamp->lock);

	write_lock_irqsave(&tstamp->lock, flags);

	timecounter_read(&tstamp->clock);

	write_unlock(&tstamp->lock);

	write_unlock_irqrestore(&tstamp->lock, flags);

	schedule_delayed_work(&tstamp->overflow_work, tstamp->overflow_period);

}
@@ -136,10 +137,11 @@ static int mlx5e_ptp_settime(struct ptp_clock_info *ptp, 
	struct mlx5e_tstamp *tstamp = container_of(ptp, struct mlx5e_tstamp,

						   ptp_info);

	u64 ns = timespec64_to_ns(ts);

	unsigned long flags;



	write_lock(&tstamp->lock);

	write_lock_irqsave(&tstamp->lock, flags);

	timecounter_init(&tstamp->clock, &tstamp->cycles, ns);

	write_unlock(&tstamp->lock);

	write_unlock_irqrestore(&tstamp->lock, flags);



	return 0;

}
@@ -150,10 +152,11 @@ static int mlx5e_ptp_gettime(struct ptp_clock_info *ptp, 
	struct mlx5e_tstamp *tstamp = container_of(ptp, struct mlx5e_tstamp,

						   ptp_info);

	u64 ns;

	unsigned long flags;



	write_lock(&tstamp->lock);

	write_lock_irqsave(&tstamp->lock, flags);

	ns = timecounter_read(&tstamp->clock);

	write_unlock(&tstamp->lock);

	write_unlock_irqrestore(&tstamp->lock, flags);



	*ts = ns_to_timespec64(ns);
@@ -164,10 +167,11 @@ static int mlx5e_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta) 
{

	struct mlx5e_tstamp *tstamp = container_of(ptp, struct mlx5e_tstamp,

						   ptp_info);

	unsigned long flags;



	write_lock(&tstamp->lock);

	write_lock_irqsave(&tstamp->lock, flags);

	timecounter_adjtime(&tstamp->clock, delta);

	write_unlock(&tstamp->lock);

	write_unlock_irqrestore(&tstamp->lock, flags);



	return 0;

}
@@ -176,6 +180,7 @@ static int mlx5e_ptp_adjfreq(struct ptp_clock_info *ptp, s32 delta) 
{

	u64 adj;

	u32 diff;

	unsigned long flags;

	int neg_adj = 0;

	struct mlx5e_tstamp *tstamp = container_of(ptp, struct mlx5e_tstamp,

						  ptp_info);
@@ -189,11 +194,11 @@ static int mlx5e_ptp_adjfreq(struct ptp_clock_info *ptp, s32 delta) 
	adj *= delta;

	diff = div_u64(adj, 1000000000ULL);



	write_lock(&tstamp->lock);

	write_lock_irqsave(&tstamp->lock, flags);

	timecounter_read(&tstamp->clock);

	tstamp->cycles.mult = neg_adj ? tstamp->nominal_c_mult - diff :

					tstamp->nominal_c_mult + diff;

	write_unlock(&tstamp->lock);

	write_unlock_irqrestore(&tstamp->lock, flags);



	return 0;

}