Fix cpuinfo init on Linux without CPU sysfs lists

cmake/external/onnxruntime_external_deps.cmake

@@ -376,6 +376,18 @@ if (CPUINFO_SUPPORTED)
         ${Patch_EXECUTABLE} -p1 < ${PROJECT_SOURCE_DIR}/patches/cpuinfo/win_arm_fp16_detection_fallback.patch
       FIND_PACKAGE_ARGS NAMES cpuinfo
     )
+  elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    message(STATUS "Applying sysfs fallback patch for cpuinfo on Linux")
+    onnxruntime_fetchcontent_declare(
+      pytorch_cpuinfo
+      URL ${DEP_URL_pytorch_cpuinfo}
+      URL_HASH SHA1=${DEP_SHA1_pytorch_cpuinfo}
+      EXCLUDE_FROM_ALL
+      PATCH_COMMAND
+        # https://github.com/microsoft/onnxruntime/issues/10038
+        ${Patch_EXECUTABLE} -p1 < ${PROJECT_SOURCE_DIR}/patches/cpuinfo/fix_missing_sysfs_fallback.patch
+      FIND_PACKAGE_ARGS NAMES cpuinfo
+    )
   else()
     onnxruntime_fetchcontent_declare(
       pytorch_cpuinfo

cmake/patches/cpuinfo/fix_missing_sysfs_fallback.patch

@@ -0,0 +1,83 @@
+diff --git a/src/linux/processors.c b/src/linux/processors.c
+index 47bee76..d0c5569 100644
+--- a/src/linux/processors.c
++++ b/src/linux/processors.c
+@@ -2,0 +3 @@
++#include <unistd.h>
+@@ -291,0 +293,22 @@
++static uint32_t cpuinfo_linux_get_max_processor_from_sysconf(
++	uint32_t max_processors_count,
++	const char* processor_list_name) {
++	const long nproc = sysconf(_SC_NPROCESSORS_ONLN);
++	if (nproc <= 0) {
++		cpuinfo_log_warning(
++			"failed to query online processors from sysconf(_SC_NPROCESSORS_ONLN) for %s",
++			processor_list_name);
++		return UINT32_MAX;
++	}
++
++	uint32_t max_processor = (uint32_t)(nproc - 1);
++	if ((uint64_t)nproc > (uint64_t)max_processors_count) {
++		cpuinfo_log_warning(
++			"online processors count %ld exceeds system limit %" PRIu32 ": truncating to the latter",
++			nproc,
++			max_processors_count);
++		max_processor = max_processors_count - 1;
++	}
++	return max_processor;
++}
++
+@@ -301 +324 @@
+-		return UINT32_MAX;
++		return cpuinfo_linux_get_max_processor_from_sysconf(max_processors_count, POSSIBLE_CPULIST_FILENAME);
+@@ -323 +346 @@
+-		return UINT32_MAX;
++		return cpuinfo_linux_get_max_processor_from_sysconf(max_processors_count, PRESENT_CPULIST_FILENAME);
+@@ -357,0 +381,31 @@
++static bool cpuinfo_linux_detect_processors_from_sysconf(
++	uint32_t max_processors_count,
++	uint32_t* processor0_flags,
++	uint32_t processor_struct_size,
++	uint32_t detected_flag,
++	const char* processor_list_name) {
++	const long nproc = sysconf(_SC_NPROCESSORS_ONLN);
++	if (nproc <= 0) {
++		cpuinfo_log_warning(
++			"failed to query online processors from sysconf(_SC_NPROCESSORS_ONLN) for %s",
++			processor_list_name);
++		return false;
++	}
++
++	uint32_t processors_count = (uint32_t)nproc;
++	if ((uint64_t)nproc > (uint64_t)max_processors_count) {
++		cpuinfo_log_warning(
++			"online processors count %ld exceeds system limit %" PRIu32 ": truncating to the latter",
++			nproc,
++			max_processors_count);
++		processors_count = max_processors_count;
++	}
++
++	for (uint32_t processor = 0; processor < processors_count; processor++) {
++		*((uint32_t*)((uintptr_t)processor0_flags + processor_struct_size * processor)) |= detected_flag;
++	}
++	cpuinfo_log_warning(
++		"falling back to sysconf(_SC_NPROCESSORS_ONLN) = %ld for %s", nproc, processor_list_name);
++	return true;
++}
++
+@@ -373 +427,6 @@
+-		return false;
++		return cpuinfo_linux_detect_processors_from_sysconf(
++			max_processors_count,
++			processor0_flags,
++			processor_struct_size,
++			possible_flag,
++			POSSIBLE_CPULIST_FILENAME);
+@@ -392 +451,6 @@
+-		return false;
++		return cpuinfo_linux_detect_processors_from_sysconf(
++			max_processors_count,
++			processor0_flags,
++			processor_struct_size,
++			present_flag,
++			PRESENT_CPULIST_FILENAME);

onnxruntime/core/platform/posix/env.cc

@@ -618,7 +618,17 @@ class PosixEnv : public Env {
   PosixEnv() {
     cpuinfo_available_ = cpuinfo_initialize();
     if (!cpuinfo_available_) {
-      LOGS_DEFAULT(INFO) << "cpuinfo_initialize failed";
+      // PosixEnv may be constructed before the logging system is initialized
+      // (e.g. via a static Env::Default() reference in the Python bindings).
+      // Using LOGS_DEFAULT here would crash with "Attempt to use DefaultLogger
+      // but none has been registered". Fall back to stderr when no logger exists.
+      if (logging::LoggingManager::HasDefaultLogger()) {
+        LOGS_DEFAULT(WARNING) << "cpuinfo_initialize failed. "
+                                 "May cause CPU EP performance degradation due to undetected CPU features.";
+      } else {
+        std::cerr << "onnxruntime warning: cpuinfo_initialize failed. "
+                     "May cause CPU EP performance degradation due to undetected CPU features.\n";
+      }
     }
   }
   bool cpuinfo_available_{false};