linux: fix accurarcy of get_nprocs and get_nprocs_conf [BZ #28865]

glibc.spec

@@ -66,7 +66,7 @@
 ##############################################################################
 Name: 	 	glibc
 Version: 	2.34
-Release: 	54
+Release: 	55
 Summary: 	The GNU libc libraries
 License:	%{all_license}
 URL: 		http://www.gnu.org/software/glibc/
@@ -189,6 +189,7 @@ Patch101: Linux-Only-generate-64-bit-timestamps-for-64-bit-tim.patch
 Patch102: socket-Do-not-use-AF_NETLINK-in-__opensock.patch
 Patch103: tst-socket-timestamp-compat.c-Check-__TIMESIZE-BZ-28.patch
 Patch104: linux-Fix-missing-__convert_scm_timestamps-BZ-28860.patch
+Patch105: linux-fix-accuracy-of-get_nprocs-and-get_nprocs_conf.patch
 
 Patch9000: turn-default-value-of-x86_rep_stosb_threshold_form_2K_to_1M.patch
 Patch9001: delete-no-hard-link-to-avoid-all_language-package-to.patch 
@@ -1292,6 +1293,9 @@ fi
 %endif
 
 %changelog
+* Wed Feb 9 2022 Qingqing Li <liqingqing3@huawei.com> - 2.34-55
+- linux: fix accurarcy of get_nprocs and get_nprocs_conf [BZ #28865]
+
 * Tue Feb 8 2022 Yang Yanchao <yangyanchao6@huawei.com> - 2.34-54
 - disable rt/tst-cpuclock2 which often fails in CI.
 

linux-fix-accuracy-of-get_nprocs-and-get_nprocs_conf.patch

@@ -0,0 +1,212 @@
+From 007e054d786be340699c634e3a3b30ab1fde1a7a Mon Sep 17 00:00:00 2001
+From: "Dmitry V. Levin" <ldv@altlinux.org>
+Date: Sat, 5 Feb 2022 08:00:00 +0000
+Subject: [PATCH] linux: fix accuracy of get_nprocs and get_nprocs_conf [BZ
+ #28865]
+
+get_nprocs() and get_nprocs_conf() use various methods to obtain an
+accurate number of processors.  Re-introduce __get_nprocs_sched() as
+a source of information, and fix the order in which these methods are
+used to return the most accurate information.  The primary source of
+information used in both functions remains unchanged.
+
+This also changes __get_nprocs_sched() error return value from 2 to 0,
+but all its users are already prepared to handle that.
+
+Old fallback order:
+  get_nprocs:
+    /sys/devices/system/cpu/online -> /proc/stat -> 2
+  get_nprocs_conf:
+    /sys/devices/system/cpu/ -> /proc/stat -> 2
+
+New fallback order:
+  get_nprocs:
+    /sys/devices/system/cpu/online -> /proc/stat -> sched_getaffinity -> 2
+  get_nprocs_conf:
+    /sys/devices/system/cpu/ -> /proc/stat -> sched_getaffinity -> 2
+
+Fixes: 342298278e ("linux: Revert the use of sched_getaffinity on get_nproc")
+Closes: BZ #28865
+Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+(cherry picked from commit e1d32b836410767270a3adf1f82b1a47e6e4cd51)
+---
+ NEWS                                  |  2 +
+ sysdeps/unix/sysv/linux/getsysstats.c | 94 ++++++++++++++++++---------
+ 2 files changed, 65 insertions(+), 31 deletions(-)
+
+diff --git a/NEWS b/NEWS
+index 87c9517e1a..aef051122e 100644
+--- a/NEWS
++++ b/NEWS
+@@ -29,6 +29,8 @@ The following bugs are resolved with this release:
+   [28349] libc: Segfault for ping -R on qemux86 caused by recvmsg()
+   [28350] libc: ping receives SIGABRT on lib32-qemux86-64 caused by
+     recvmsg()
++  [28865] linux: _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are inaccurate
++    without /sys and /proc
+ 
+ 
+ Version 2.34
+diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c
+index 7babd947aa..327802b14c 100644
+--- a/sysdeps/unix/sysv/linux/getsysstats.c
++++ b/sysdeps/unix/sysv/linux/getsysstats.c
+@@ -51,9 +51,8 @@ __get_nprocs_sched (void)
+        is an arbitrary values assuming such systems should be rare and there
+        is no offline cpus.  */
+     return max_num_cpus;
+-  /* Some other error.  2 is conservative (not a uniprocessor system, so
+-     atomics are needed). */
+-  return 2;
++  /* Some other error.  */
++  return 0;
+ }
+ 
+ static char *
+@@ -109,22 +108,19 @@ next_line (int fd, char *const buffer, char **cp, char **re,
+ }
+ 
+ static int
+-get_nproc_stat (char *buffer, size_t buffer_size)
++get_nproc_stat (void)
+ {
++  enum { buffer_size = 1024 };
++  char buffer[buffer_size];
+   char *buffer_end = buffer + buffer_size;
+   char *cp = buffer_end;
+   char *re = buffer_end;
+-
+-  /* Default to an SMP system in case we cannot obtain an accurate
+-     number.  */
+-  int result = 2;
++  int result = 0;
+ 
+   const int flags = O_RDONLY | O_CLOEXEC;
+   int fd = __open_nocancel ("/proc/stat", flags);
+   if (fd != -1)
+     {
+-      result = 0;
+-
+       char *l;
+       while ((l = next_line (fd, buffer, &cp, &re, buffer_end)) != NULL)
+ 	/* The current format of /proc/stat has all the cpu* entries
+@@ -140,8 +136,8 @@ get_nproc_stat (char *buffer, size_t buffer_size)
+   return result;
+ }
+ 
+-int
+-__get_nprocs (void)
++static int
++get_nprocs_cpu_online (void)
+ {
+   enum { buffer_size = 1024 };
+   char buffer[buffer_size];
+@@ -180,7 +176,8 @@ __get_nprocs (void)
+ 		  }
+ 	      }
+ 
+-	    result += m - n + 1;
++	    if (m >= n)
++	      result += m - n + 1;
+ 
+ 	    l = endp;
+ 	    if (l < re && *l == ',')
+@@ -189,28 +186,18 @@ __get_nprocs (void)
+ 	while (l < re && *l != '\n');
+ 
+       __close_nocancel_nostatus (fd);
+-
+-      if (result > 0)
+-	return result;
+     }
+ 
+-  return get_nproc_stat (buffer, buffer_size);
++  return result;
+ }
+-libc_hidden_def (__get_nprocs)
+-weak_alias (__get_nprocs, get_nprocs)
+-
+ 
+-/* On some architectures it is possible to distinguish between configured
+-   and active cpus.  */
+-int
+-__get_nprocs_conf (void)
++static int
++get_nprocs_cpu (void)
+ {
+-  /* Try to use the sysfs filesystem.  It has actual information about
+-     online processors.  */
++  int count = 0;
+   DIR *dir = __opendir ("/sys/devices/system/cpu");
+   if (dir != NULL)
+     {
+-      int count = 0;
+       struct dirent64 *d;
+ 
+       while ((d = __readdir64 (dir)) != NULL)
+@@ -225,12 +212,57 @@ __get_nprocs_conf (void)
+ 
+       __closedir (dir);
+ 
+-      return count;
+     }
++  return count;
++}
+ 
+-  enum { buffer_size = 1024 };
+-  char buffer[buffer_size];
+-  return get_nproc_stat (buffer, buffer_size);
++static int
++get_nprocs_fallback (void)
++{
++  int result;
++
++  /* Try /proc/stat first.  */
++  result = get_nproc_stat ();
++  if (result != 0)
++    return result;
++
++  /* Try sched_getaffinity.  */
++  result = __get_nprocs_sched ();
++  if (result != 0)
++    return result;
++
++  /* We failed to obtain an accurate number.  Be conservative: return
++     the smallest number meaning that this is not a uniprocessor system,
++     so atomics are needed.  */
++  return 2;
++}
++
++int
++__get_nprocs (void)
++{
++  /* Try /sys/devices/system/cpu/online first.  */
++  int result = get_nprocs_cpu_online ();
++  if (result != 0)
++    return result;
++
++  /* Fall back to /proc/stat and sched_getaffinity.  */
++  return get_nprocs_fallback ();
++}
++libc_hidden_def (__get_nprocs)
++weak_alias (__get_nprocs, get_nprocs)
++
++/* On some architectures it is possible to distinguish between configured
++   and active cpus.  */
++int
++__get_nprocs_conf (void)
++{
++  /* Try /sys/devices/system/cpu/ first.  */
++  int result = get_nprocs_cpu ();
++  if (result != 0)
++    return result;
++
++  /* Fall back to /proc/stat and sched_getaffinity.  */
++  return get_nprocs_fallback ();
+ }
+ libc_hidden_def (__get_nprocs_conf)
+ weak_alias (__get_nprocs_conf, get_nprocs_conf)
+-- 
+2.27.0
+