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llama.cpp
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metal: handle command buffer failures gracefully in synchronize (#20306) 

Replace GGML_ABORT("fatal error") in ggml_metal_synchronize() with
error flag + return. This aligns synchronize error handling with
graph_compute, which already returns GGML_STATUS_FAILED for the same
condition.

When a command buffer fails (e.g., iOS GPU access revocation during
backgrounding, macOS eGPU disconnect, OOM), the backend enters an
error state instead of killing the host process. Subsequent
graph_compute calls return GGML_STATUS_FAILED immediately. Recovery
requires recreating the backend.

Failed extra command buffers are properly released on the error path
to avoid Metal object leaks.
This commit is contained in:
Julian Pscheid 2026-03-09 23:32:24 -07:00 committed by GitHub
parent 1dab5f5a44
commit 1a5631beaa
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GPG Key ID: B5690EEEBB952194
1 changed files with 22 additions and 2 deletions
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24
ggml/src/ggml-metal/ggml-metal-context.m
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@ -75,6 +75,10 @@ struct ggml_metal {
// abort ggml_metal_graph_compute if callback returns true
ggml_abort_callback abort_callback;
void * abort_callback_data;
// error state - set when a command buffer fails during synchronize
// once set, graph_compute will return GGML_STATUS_FAILED until the backend is recreated
bool has_error;
};
ggml_metal_t ggml_metal_init(ggml_metal_device_t dev) {
@ -158,6 +162,8 @@ ggml_metal_t ggml_metal_init(ggml_metal_device_t dev) {
res->capture_started = false;
res->capture_scope = nil;
res->has_error = false;
res->gf = nil;
res->encode_async = nil;
for (int i = 0; i < GGML_METAL_MAX_COMMAND_BUFFERS; ++i) {
@ -246,7 +252,8 @@ void ggml_metal_synchronize(ggml_metal_t ctx) {
if (status == MTLCommandBufferStatusError) {
GGML_LOG_ERROR("error: %s\n", [[cmd_buf error].localizedDescription UTF8String]);
}
GGML_ABORT("fatal error");
ctx->has_error = true;
return;
}
}
}
@ -262,7 +269,15 @@ void ggml_metal_synchronize(ggml_metal_t ctx) {
if (status == MTLCommandBufferStatusError) {
GGML_LOG_ERROR("error: %s\n", [[cmd_buf error].localizedDescription UTF8String]);
}
GGML_ABORT("fatal error");
// release this and all remaining command buffers before returning
for (size_t j = i; j < ctx->cmd_bufs_ext.count; ++j) {
[ctx->cmd_bufs_ext[j] release];
}
[ctx->cmd_bufs_ext removeAllObjects];
ctx->has_error = true;
return;
}
[cmd_buf release];
@ -414,6 +429,11 @@ bool ggml_metal_cpy_tensor_async(ggml_metal_t ctx_src, ggml_metal_t ctx_dst, con
}
enum ggml_status ggml_metal_graph_compute(ggml_metal_t ctx, struct ggml_cgraph * gf) {
if (ctx->has_error) {
GGML_LOG_ERROR("%s: backend is in error state from a previous command buffer failure - recreate the backend to recover\n", __func__);
return GGML_STATUS_FAILED;
}
// number of nodes encoded by the main thread (empirically determined)
const int n_main = MAX(64, 0.1*gf->n_nodes);