gru: add comments raised in previous code reviews

Add comments from previous code reviews.  The comments help explain some
of the more esoteric aspects of the driver.

Move a free() to the other side of an unlock.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 8 insertions, 1 deletions

diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index 679e01778286..2605edfbaebe 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -733,6 +733,11 @@ long gru_get_gseg_statistics(unsigned long arg)
         if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
                 return -EFAULT;
 
+        /*
+         * The library creates arrays of contexts for threaded programs.
+         * If no gts exists in the array, the context has never been used & all
+         * statistics are implicitly 0.
+         */
         gts = gru_find_lock_gts(req.gseg);
         if (gts) {
                 memcpy(&req.stats, &gts->ustats, sizeof(gts->ustats));
diff --git a/drivers/misc/sgi-gru/grukservices.c b/drivers/misc/sgi-gru/grukservices.c
index d2b149facda1..306855cc80fe 100644
--- a/drivers/misc/sgi-gru/grukservices.c
+++ b/drivers/misc/sgi-gru/grukservices.c
@@ -200,13 +200,15 @@ static int gru_free_kernel_contexts(void)
                 bs = gru_base[bid];
                 if (!bs)
                         continue;
+
+                /* Ignore busy contexts. Don't want to block here.  */
                 if (down_write_trylock(&bs->bs_kgts_sema)) {
                         kgts = bs->bs_kgts;
                         if (kgts && kgts->ts_gru)
                                 gru_unload_context(kgts, 0);
-                        kfree(kgts);
                         bs->bs_kgts = NULL;
                         up_write(&bs->bs_kgts_sema);
+                        kfree(kgts);
                 } else {
                         ret++;
                 }