Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=36ddbb1380f282b4280c57efdb646dd8647a789f
Commit: 36ddbb1380f282b4280c57efdb646dd8647a789f
Parent: 8b0d3121a0b2cf91768ecef635e241b6abc3f1da
Author: Andre Detsch <[EMAIL PROTECTED]>
AuthorDate: Wed Sep 19 14:38:12 2007 +1000
Committer: Paul Mackerras <[EMAIL PROTECTED]>
CommitDate: Wed Sep 19 15:12:16 2007 +1000
[POWERPC] spufs: Fix race condition on gang->aff_ref_spu
Affinity reference point location (gang->aff_ref_spu) is reset
when the whole gang is descheduled. However, the last member of
a gang can be descheduled while we are trying to schedule another
member of the gang. This was leading to a race condition, and
the code was using gang->aff_ref_spu in an unsafe manner.
By holding the gang->aff_mutex a little bit longer, and increment
gang->aff_sched_count (which controls when gang->aff_ref_spu
should be reset) a little bit earlier, the problem is fixed.
Signed-off-by: Andre Detsch <[EMAIL PROTECTED]>
Signed-off-by: Jeremy Kerr <[EMAIL PROTECTED]>
Signed-off-by: Paul Mackerras <[EMAIL PROTECTED]>
---
arch/powerpc/platforms/cell/spufs/sched.c | 49 +++++++++++++++++++----------
1 files changed, 32 insertions(+), 17 deletions(-)
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c
b/arch/powerpc/platforms/cell/spufs/sched.c
index c784edd..17806e0 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -230,8 +230,6 @@ static void spu_bind_context(struct spu *spu, struct
spu_context *ctx)
if (ctx->flags & SPU_CREATE_NOSCHED)
atomic_inc(&cbe_spu_info[spu->node].reserved_spus);
- if (!list_empty(&ctx->aff_list))
- atomic_inc(&ctx->gang->aff_sched_count);
ctx->stats.slb_flt_base = spu->stats.slb_flt;
ctx->stats.class2_intr_base = spu->stats.class2_intr;
@@ -392,7 +390,6 @@ static int has_affinity(struct spu_context *ctx)
if (list_empty(&ctx->aff_list))
return 0;
- mutex_lock(&gang->aff_mutex);
if (!gang->aff_ref_spu) {
if (!(gang->aff_flags & AFF_MERGED))
aff_merge_remaining_ctxs(gang);
@@ -400,7 +397,6 @@ static int has_affinity(struct spu_context *ctx)
aff_set_offsets(gang);
aff_set_ref_point_location(gang);
}
- mutex_unlock(&gang->aff_mutex);
return gang->aff_ref_spu != NULL;
}
@@ -418,9 +414,16 @@ static void spu_unbind_context(struct spu *spu, struct
spu_context *ctx)
if (spu->ctx->flags & SPU_CREATE_NOSCHED)
atomic_dec(&cbe_spu_info[spu->node].reserved_spus);
- if (!list_empty(&ctx->aff_list))
- if (atomic_dec_and_test(&ctx->gang->aff_sched_count))
- ctx->gang->aff_ref_spu = NULL;
+
+ if (ctx->gang){
+ mutex_lock(&ctx->gang->aff_mutex);
+ if (has_affinity(ctx)) {
+ if (atomic_dec_and_test(&ctx->gang->aff_sched_count))
+ ctx->gang->aff_ref_spu = NULL;
+ }
+ mutex_unlock(&ctx->gang->aff_mutex);
+ }
+
spu_switch_notify(spu, NULL);
spu_unmap_mappings(ctx);
spu_save(&ctx->csa, spu);
@@ -511,20 +514,32 @@ static void spu_prio_wait(struct spu_context *ctx)
static struct spu *spu_get_idle(struct spu_context *ctx)
{
- struct spu *spu;
+ struct spu *spu, *aff_ref_spu;
int node, n;
- if (has_affinity(ctx)) {
- node = ctx->gang->aff_ref_spu->node;
+ if (ctx->gang) {
+ mutex_lock(&ctx->gang->aff_mutex);
+ if (has_affinity(ctx)) {
+ aff_ref_spu = ctx->gang->aff_ref_spu;
+ atomic_inc(&ctx->gang->aff_sched_count);
+ mutex_unlock(&ctx->gang->aff_mutex);
+ node = aff_ref_spu->node;
- mutex_lock(&cbe_spu_info[node].list_mutex);
- spu = ctx_location(ctx->gang->aff_ref_spu, ctx->aff_offset,
node);
- if (spu && spu->alloc_state == SPU_FREE)
- goto found;
- mutex_unlock(&cbe_spu_info[node].list_mutex);
- return NULL;
- }
+ mutex_lock(&cbe_spu_info[node].list_mutex);
+ spu = ctx_location(aff_ref_spu, ctx->aff_offset, node);
+ if (spu && spu->alloc_state == SPU_FREE)
+ goto found;
+ mutex_unlock(&cbe_spu_info[node].list_mutex);
+ mutex_lock(&ctx->gang->aff_mutex);
+ if (atomic_dec_and_test(&ctx->gang->aff_sched_count))
+ ctx->gang->aff_ref_spu = NULL;
+ mutex_unlock(&ctx->gang->aff_mutex);
+
+ return NULL;
+ }
+ mutex_unlock(&ctx->gang->aff_mutex);
+ }
node = cpu_to_node(raw_smp_processor_id());
for (n = 0; n < MAX_NUMNODES; n++, node++) {
node = (node < MAX_NUMNODES) ? node : 0;
-
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