IB/ipath: Head of Line blocking vs forward progress of user apps

There's a conflict between our need to quiesce PSM-based applications
to avoid HoL blocking when the IB link goes down and the apps' desire
to remain running so that their quiescence timout mechanism can keep
running.

The compromise is to STOP the processes for a fixed period of time and
then alternate between CONT and STOP until the link is again active.

If there are poor interactions with subnet manager configuration at a
given site, the interval can be adjusted via a module paramter.

Signed-off-by: John Gregor <john.gregor@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/infiniband/hw/ipath/ipath_kernel.h b/drivers/infiniband/hw/ipath/ipath_kernel.h
index 70c0a0dd693..caee731b670 100644
--- a/drivers/infiniband/hw/ipath/ipath_kernel.h
+++ b/drivers/infiniband/hw/ipath/ipath_kernel.h
@@ -427,6 +427,11 @@ struct ipath_devdata {
 
         unsigned long ipath_ureg_align; /* user register alignment */
 
+        /* HoL blocking / user app forward-progress state */
+        unsigned          ipath_hol_state;
+        unsigned          ipath_hol_next;
+        struct timer_list ipath_hol_timer;
+
         /*
          * Shadow copies of registers; size indicates read access size.
          * Most of them are readonly, but some are write-only register,
@@ -706,6 +711,13 @@ struct ipath_devdata {
         u16 ipath_jint_max_packets;     /* max packets across all ports */
 };
 
+/* ipath_hol_state values (stopping/starting user proc, send flushing) */
+#define IPATH_HOL_UP       0
+#define IPATH_HOL_DOWN     1
+/* ipath_hol_next toggle values, used when hol_state IPATH_HOL_DOWN */
+#define IPATH_HOL_DOWNSTOP 0
+#define IPATH_HOL_DOWNCONT 1
+
 /* Private data for file operations */
 struct ipath_filedata {
         struct ipath_portdata *pd;
@@ -775,6 +787,9 @@ int ipath_set_lid(struct ipath_devdata *, u32, u8);
 int ipath_set_rx_pol_inv(struct ipath_devdata *dd, u8 new_pol_inv);
 void ipath_enable_armlaunch(struct ipath_devdata *);
 void ipath_disable_armlaunch(struct ipath_devdata *);
+void ipath_hol_down(struct ipath_devdata *);
+void ipath_hol_up(struct ipath_devdata *);
+void ipath_hol_event(unsigned long);
 
 /* for use in system calls, where we want to know device type, etc. */
 #define port_fp(fp) ((struct ipath_filedata *)(fp)->private_data)->pd
@@ -830,6 +845,7 @@ void ipath_disable_armlaunch(struct ipath_devdata *);
                 /* Suppress heartbeat, even if turning off loopback */
 #define IPATH_NO_HRTBT      0x1000000
 #define IPATH_HAS_MULT_IB_SPEED 0x8000000
+#define IPATH_IB_FORCE_NOTIFY 0x80000000 /* force notify on next ib change */
 
 /* Bits in GPIO for the added interrupts */
 #define IPATH_GPIO_PORT0_BIT 2
@@ -1030,6 +1046,21 @@ static inline u32 ipath_ib_linktrstate(struct ipath_devdata *dd, u64 ibcs)
 }
 
 /*
+ * from contents of IBCStatus (or a saved copy), return logical link state
+ * combination of link state and linktraining state (down, active, init,
+ * arm, etc.
+ */
+static inline u32 ipath_ib_state(struct ipath_devdata *dd, u64 ibcs)
+{
+        u32 ibs;
+        ibs = (u32)(ibcs >> INFINIPATH_IBCS_LINKTRAININGSTATE_SHIFT) &
+                dd->ibcs_lts_mask;
+        ibs |= (u32)(ibcs &
+                (INFINIPATH_IBCS_LINKSTATE_MASK << dd->ibcs_ls_shift));
+        return ibs;
+}
+
+/*
  * sysfs interface.
  */