From 3f48188a45874e65d0fa3dc1d7021c5e78ef2a08 Mon Sep 17 00:00:00 2001
From: ckolivas <kernel@kolivas.org>
Date: Thu, 12 Feb 2026 20:48:54 +1100
Subject: [PATCH] Deal with number of available CPUs rather than number of
 online CPUs to cope with CPU affinity being set.

---
 lrzip.c         | 23 ++++++++++++++++++++++-
 lrzip_private.h |  6 ------
 main.c          |  2 +-
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/lrzip.c b/lrzip.c
index e004cf9..ac3c923 100644
--- a/lrzip.c
+++ b/lrzip.c
@@ -1464,6 +1464,27 @@ error:
 	return false;
 }
 
+static int get_available_cpus(void)
+{
+	long sys;
+#ifdef __linux__
+	cpu_set_t mask;
+	CPU_ZERO(&mask);
+
+	if (sched_getaffinity(0, sizeof(mask), &mask) == 0) {
+		int count = CPU_COUNT(&mask);
+		if (count > 0)
+		    return count;
+	}
+#endif
+	/* Fallback to system-wide online CPUs */
+	sys = sysconf(_SC_NPROCESSORS_ONLN);
+	if (sys > 0)
+		return (int)sys;
+
+	return 1;  /* Absolute minimum */
+}
+
 bool initialise_control(rzip_control *control)
 {
 	time_t now_t, tdiff;
@@ -1481,7 +1502,7 @@ bool initialise_control(rzip_control *control)
 	if (unlikely(control->ramsize == -1))
 		return false;
 	/* for testing single CPU */
-	control->threads = PROCESSORS;	/* get CPUs for LZMA */
+	control->threads = get_available_cpus();	/* get CPUs for LZMA */
 	control->page_size = PAGE_SIZE;
 	control->nice_val = 19;
 
diff --git a/lrzip_private.h b/lrzip_private.h
index 689025d..622ffee 100644
--- a/lrzip_private.h
+++ b/lrzip_private.h
@@ -249,12 +249,6 @@ typedef sem_t cksem_t;
 
 #define one_g (1000 * 1024 * 1024)
 
-#if defined(NOTHREAD) || !defined(_SC_NPROCESSORS_ONLN)
-# define PROCESSORS (1)
-#else
-# define PROCESSORS (sysconf(_SC_NPROCESSORS_ONLN))
-#endif
-
 #ifndef PAGE_SIZE
 # ifdef _SC_PAGE_SIZE
 #  define PAGE_SIZE (sysconf(_SC_PAGE_SIZE))
diff --git a/main.c b/main.c
index 8e0309b..796916b 100644
--- a/main.c
+++ b/main.c
@@ -163,7 +163,7 @@ static void show_summary(void)
 		if (!TEST_ONLY)
 			print_verbose("The following options are in effect for this %s.\n",
 				      DECOMPRESS ? "DECOMPRESSION" : "COMPRESSION");
-		print_verbose("Threading is %s. Number of CPUs detected: %d\n", control->threads > 1? "ENABLED" : "DISABLED",
+		print_verbose("Threading is %s. Number of CPUs available detected: %d\n", control->threads > 1? "ENABLED" : "DISABLED",
 			      control->threads);
 		print_verbose("Detected %"PRId64" bytes ram\n", control->ramsize);
 		print_verbose("Compression level %d\n", control->compression_level);