| 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 |
| |