From: Jeff Bolz <redacted>
Date: Sun, 14 Dec 2025 08:00:00 +0000 (-0600)
Subject: vulkan: Fix data race/hang in scalar/cm1 flash attention (#17887)
X-Git-Tag: upstream/0.0.7446~48
X-Git-Url: https://git.djapps.eu/?a=commitdiff_plain;h=3238b1400cf4f0f174c39579d92ce1a8ddb68110;p=pkg%2Fggml%2Fsources%2Fllama.cpp

vulkan: Fix data race/hang in scalar/cm1 flash attention (#17887)
---

diff --git a/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn.comp b/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn.comp
index 4bef48b0..0379e5d5 100644
--- a/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn.comp
+++ b/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn.comp
@@ -256,6 +256,9 @@ void main() {
         barrier();
     }
 
+    // prevent race on tmpsh
+    barrier();
+
     // reduce across threads
 
     [[unroll]] for (uint32_t r = 0; r < Br; ++r) {
diff --git a/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm1.comp b/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm1.comp
index cd82e4ab..c995ab14 100644
--- a/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm1.comp
+++ b/ggml/src/ggml-vulkan/vulkan-shaders/flash_attn_cm1.comp
@@ -302,6 +302,9 @@ void main() {
         barrier();
     }
 
+    // prevent race on tmpsh
+    barrier();
+
     // reduce across threads
 
     float rowmaxf[rows_per_thread], eMf[rows_per_thread], Moldf[rows_per_thread];