diff options
Diffstat (limited to 'linux-fix-accuracy-of-get_nprocs-and-get_nprocs_conf.patch')
| -rw-r--r-- | linux-fix-accuracy-of-get_nprocs-and-get_nprocs_conf.patch | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/linux-fix-accuracy-of-get_nprocs-and-get_nprocs_conf.patch b/linux-fix-accuracy-of-get_nprocs-and-get_nprocs_conf.patch new file mode 100644 index 0000000..d16fa75 --- /dev/null +++ b/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 + |