lttng-ust: backport musl workaround

musl implementation for _SC_NPROCESSORS_CONF is a bit fishy. [1] https://www.openwall.com/lists/musl/2019/03/15/5 Anyway, we implemented a fallback. This patch should be gone by next recipe update. (From OE-Core rev: 5feddda9ac7ea72eac3d5a83251fa023b67aebce) Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
2026-05-09 05:29:32 +00:00 · 2019-04-04 21:47:41 +00:00
parent 8e9a0fe61f
commit 9c01b82269
2 changed files with 111 additions and 0 deletions
@@ -0,0 +1,109 @@
+From 5de7c318804a7b1edce8562d4891b4c74aac0677 Mon Sep 17 00:00:00 2001
+From: Michael Jeanson <mjeanson@efficios.com>
+Date: Wed, 20 Mar 2019 11:07:35 -0400
+Subject: [PATCH] compat: work around broken _SC_NPROCESSORS_CONF on MUSL libc
+
+On MUSL libc the _SC_NPROCESSORS_CONF sysconf will report the number of
+CPUs allocated to the task based on the affinity mask instead of the
+total number of CPUs configured on the system.
+
+Upstream-Status: Accepted [1] [5de7c318804a7b1edce8562d4891b4c74aac0677]
+[1] https://lists.lttng.org/pipermail/lttng-dev/2019-March/028616.html
+
+Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
+Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+---
+ libringbuffer/smp.c | 66 +++++++++++++++++++++++++++++++++++++++++++++
+ 1 file changed, 66 insertions(+)
+
+diff --git a/libringbuffer/smp.c b/libringbuffer/smp.c
+index 9e7114be..656a75da 100644
+--- a/libringbuffer/smp.c
+++ b/libringbuffer/smp.c
+@@ -2,6 +2,7 @@
+  * libringbuffer/smp.c
+  *
+  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
+  *
+  * This library is free software; you can redistribute it and/or
+  * modify it under the terms of the GNU Lesser General Public
+@@ -26,6 +27,7 @@
+ 
+ int __num_possible_cpus;
+ 
+#if (defined(__GLIBC__) || defined( __UCLIBC__))
+ void _get_num_possible_cpus(void)
+ {
+ 	int result;
+@@ -43,3 +45,67 @@ void _get_num_possible_cpus(void)
+ 		return;
+ 	__num_possible_cpus = result;
+ }
+
+#else
+
+/*
+ * The MUSL libc implementation of the _SC_NPROCESSORS_CONF sysconf does not
+ * return the number of configured CPUs in the system but relies on the cpu
+ * affinity mask of the current task.
+ *
+ * So instead we use a strategy similar to GLIBC's, counting the cpu
+ * directories in "/sys/devices/system/cpu" and fallback on the value from
+ * sysconf if it fails.
+ */
+
+#include <dirent.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#define __max(a,b) ((a)>(b)?(a):(b))
+
+void _get_num_possible_cpus(void)
+{
+	int result, count = 0;
+	DIR *cpudir;
+	struct dirent *entry;
+
+	cpudir = opendir("/sys/devices/system/cpu");
+	if (cpudir == NULL)
+		goto end;
+
+	/*
+	 * Count the number of directories named "cpu" followed by and
+	 * integer. This is the same strategy as glibc uses.
+	 */
+	while ((entry = readdir(cpudir))) {
+		if (entry->d_type == DT_DIR &&
+			strncmp(entry->d_name, "cpu", 3) == 0) {
+
+			char *endptr;
+			unsigned long cpu_num;
+
+			cpu_num = strtoul(entry->d_name + 3, &endptr, 10);
+			if ((cpu_num < ULONG_MAX) && (endptr != entry->d_name + 3)
+					&& (*endptr == '\0')) {
+				count++;
+			}
+		}
+	}
+
+end:
+	/*
+	 * Get the sysconf value as a fallback. Keep the highest number.
+	 */
+	result = __max(sysconf(_SC_NPROCESSORS_CONF), count);
+
+	/*
+	 * If both methods failed, don't store the value.
+	 */
+	if (result < 1)
+		return;
+	__num_possible_cpus = result;
+}
+#endif
+-- 
+2.17.1
+
@@ -27,7 +27,9 @@ PE = "2"

 SRC_URI = "https://lttng.org/files/lttng-ust/lttng-ust-${PV}.tar.bz2 \
           file://lttng-ust-doc-examples-disable.patch \
+	   file://0001-compat-work-around-broken-_SC_NPROCESSORS_CONF-on-MU.patch \
          "
+
 SRC_URI[md5sum] = "ffcfa8c1ba9a52f002d240e936e9afa2"
 SRC_URI[sha256sum] = "9e8420f90d5f963f7aa32bc6d44adc1e491136f687c69ffb7a3075d33b40852b"