[PATCH net V1 3/7] net/mlx5e: Fix soft lockup when HW Timestamping is enabled

[Saeed Mahameed]

From: Eran Ben Elisha <era...@mellanox.com>

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: ef9814deafd0 ('net/mlx5e: Add HW timestamping (TS) support')
Signed-off-by: Eran Ben Elisha <era...@mellanox.com>
Signed-off-by: Saeed Mahameed <sae...@mellanox.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_clock.c |   25 ++++++++++++--------
 1 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_clock.c 
b/drivers/net/ethernet/mellanox/mlx5/core/en_clock.c
index be65435..2018eeb 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_clock.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_clock.c
@@ -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;
 }
-- 
1.7.1