From e43320ddc3a316e3410d6dde56062cf8968ea284 Mon Sep 17 00:00:00 2001 From: Nathan Hjelm Date: Tue, 2 Oct 2018 15:52:45 -0600 Subject: [PATCH 38/52] btl/vader: ensure the fast box tag is always read first On some platfoms reading a 64-bit value is non-atomic and it is possible that the two 32-bit values are read in the wrong order. To ensure the tag is always read first this commit reads the tag before reading the full 64-bit value. Signed-off-by: Nathan Hjelm (cherry picked from commit 66a7dc4c72cb25df67e7f872bee7a20b5fa9c763) --- opal/mca/btl/vader/btl_vader_fbox.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/opal/mca/btl/vader/btl_vader_fbox.h b/opal/mca/btl/vader/btl_vader_fbox.h index df1fb92..6df9a2d 100644 --- a/opal/mca/btl/vader/btl_vader_fbox.h +++ b/opal/mca/btl/vader/btl_vader_fbox.h @@ -56,6 +56,16 @@ static inline void mca_btl_vader_fbox_set_header (mca_btl_vader_fbox_hdr_t *hdr, hdr->data.tag = tag; } +static inline mca_btl_vader_fbox_hdr_t mca_btl_vader_fbox_read_header (mca_btl_vader_fbox_hdr_t *hdr) +{ + mca_btl_vader_fbox_hdr_t tmp; + uint16_t tag = hdr->data.tag; + opal_atomic_rmb (); + tmp.ival = hdr->ival; + tmp.data.tag = tag; + return tmp; +} + /* attempt to reserve a contiguous segment from the remote ep */ static inline bool mca_btl_vader_fbox_sendi (mca_btl_base_endpoint_t *ep, unsigned char tag, void * restrict header, const size_t header_size, @@ -175,7 +185,7 @@ static inline bool mca_btl_vader_check_fboxes (void) int poll_count; for (poll_count = 0 ; poll_count <= MCA_BTL_VADER_POLL_COUNT ; ++poll_count) { - const mca_btl_vader_fbox_hdr_t hdr = {.ival = MCA_BTL_VADER_FBOX_HDR(ep->fbox_in.buffer + start)->ival}; + const mca_btl_vader_fbox_hdr_t hdr = mca_btl_vader_fbox_read_header (MCA_BTL_VADER_FBOX_HDR(ep->fbox_in.buffer + start)); /* check for a valid tag a sequence number */ if (0 == hdr.data.tag || hdr.data.seq != ep->fbox_in.seq) { -- 1.8.3.1