[Patch 25/29] GRU - Fix bug in allocation of kernel contexts

steiner
2009-11-24T15:09:31Z

[-- Attachment #1: uv_gru_kservices_bug --]
[-- Type: text/plain, Size: 1710 bytes --]

From: Jack Steiner <steiner@sgi.com>

Fix a bug in the assignment of GRU contexts used for kernel
functions. If a sleep occurs on the wait for a semaphore, the thread
could switch cpus and allocate resources on the wrong blade.

Signed-off-by: Jack Steiner <steiner@sgi.com>

---
drivers/misc/sgi-gru/grukservices.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

Index: linux/drivers/misc/sgi-gru/grukservices.c
===================================================================
--- linux.orig/drivers/misc/sgi-gru/grukservices.c 2009-11-20 09:32:35.000000000 -0600
+++ linux/drivers/misc/sgi-gru/grukservices.c 2009-11-20 09:32:37.000000000 -0600
@@ -221,13 +221,21 @@ static int gru_free_kernel_contexts(void
static struct gru_blade_state *gru_lock_kernel_context(int blade_id)
{
struct gru_blade_state *bs;
+ int bid;

STAT(lock_kernel_context);
- bs = gru_base[blade_id];
+again:
+ bid = blade_id < 0 ? uv_numa_blade_id() : blade_id;
+ bs = gru_base[bid];

+ /* Handle the case where migration occured while waiting for the sema */
down_read(&bs->bs_kgts_sema);
+ if (blade_id < 0 && bid != uv_numa_blade_id()) {
+ up_read(&bs->bs_kgts_sema);
+ goto again;
+ }
if (!bs->bs_kgts || !bs->bs_kgts->ts_gru)
- gru_load_kernel_context(bs, blade_id);
+ gru_load_kernel_context(bs, bid);
return bs;

}
@@ -256,7 +264,7 @@ static int gru_get_cpu_resources(int dsr

BUG_ON(dsr_bytes > GRU_NUM_KERNEL_DSR_BYTES);
preempt_disable();
- bs = gru_lock_kernel_context(uv_numa_blade_id());
+ bs = gru_lock_kernel_context(-1);
lcpu = uv_blade_processor_id();
*cb = bs->kernel_cb + lcpu * GRU_HANDLE_STRIDE;
*dsr = bs->kernel_dsr + lcpu * GRU_NUM_KERNEL_DSR_BYTES;