diff options
Diffstat (limited to 'linux-Revert-the-use-of-sched_getaffinity-on-get_npr.patch')
| -rw-r--r-- | linux-Revert-the-use-of-sched_getaffinity-on-get_npr.patch | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/linux-Revert-the-use-of-sched_getaffinity-on-get_npr.patch b/linux-Revert-the-use-of-sched_getaffinity-on-get_npr.patch new file mode 100644 index 0000000..17a7a5c --- /dev/null +++ b/linux-Revert-the-use-of-sched_getaffinity-on-get_npr.patch @@ -0,0 +1,206 @@ +From 342298278eabc75baabcaced110a11a02c3d3580 Mon Sep 17 00:00:00 2001 +From: Adhemerval Zanella <adhemerval.zanella@linaro.org> +Date: Mon, 6 Sep 2021 14:19:51 -0300 +Subject: [PATCH] linux: Revert the use of sched_getaffinity on get_nproc (BZ + #28310) + +The use of sched_getaffinity on get_nproc and +sysconf (_SC_NPROCESSORS_ONLN) done in 903bc7dcc2acafc40 (BZ #27645) +breaks the top command in common hypervisor configurations and also +other monitoring tools. + +The main issue using sched_getaffinity changed the symbols semantic +from system-wide scope of online CPUs to per-process one (which can +be changed with kernel cpusets or book parameters in VM). + +This patch reverts mostly of the 903bc7dcc2acafc40, with the +exceptions: + + * No more cached values and atomic updates, since they are inherent + racy. + + * No /proc/cpuinfo fallback, since /proc/stat is already used and + it would require to revert more arch-specific code. + + * The alloca is replace with a static buffer of 1024 bytes. + +So the implementation first consult the sysfs, and fallbacks to procfs. + +Checked on x86_64-linux-gnu. + +Reviewed-by: Florian Weimer <fweimer@redhat.com> +--- + sysdeps/unix/sysv/linux/getsysstats.c | 139 ++++++++++++++++++++++++++++++++-- + 1 file changed, 134 insertions(+), 5 deletions(-) + +diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c +index 1e3d886..15ad91c 100644 +--- a/sysdeps/unix/sysv/linux/getsysstats.c ++++ b/sysdeps/unix/sysv/linux/getsysstats.c +@@ -17,6 +17,8 @@ + <https://www.gnu.org/licenses/>. */ + + #include <array_length.h> ++#include <assert.h> ++#include <ctype.h> + #include <dirent.h> + #include <errno.h> + #include <ldsodefs.h> +@@ -29,7 +31,7 @@ + #include <sysdep.h> + + int +-__get_nprocs (void) ++__get_nprocs_sched (void) + { + enum + { +@@ -52,14 +54,141 @@ __get_nprocs (void) + atomics are needed). */ + return 2; + } +-libc_hidden_def (__get_nprocs) +-weak_alias (__get_nprocs, get_nprocs) ++ ++static char * ++next_line (int fd, char *const buffer, char **cp, char **re, ++ char *const buffer_end) ++{ ++ char *res = *cp; ++ char *nl = memchr (*cp, '\n', *re - *cp); ++ if (nl == NULL) ++ { ++ if (*cp != buffer) ++ { ++ if (*re == buffer_end) ++ { ++ memmove (buffer, *cp, *re - *cp); ++ *re = buffer + (*re - *cp); ++ *cp = buffer; ++ ++ ssize_t n = __read_nocancel (fd, *re, buffer_end - *re); ++ if (n < 0) ++ return NULL; ++ ++ *re += n; ++ ++ nl = memchr (*cp, '\n', *re - *cp); ++ while (nl == NULL && *re == buffer_end) ++ { ++ /* Truncate too long lines. */ ++ *re = buffer + 3 * (buffer_end - buffer) / 4; ++ n = __read_nocancel (fd, *re, buffer_end - *re); ++ if (n < 0) ++ return NULL; ++ ++ nl = memchr (*re, '\n', n); ++ **re = '\n'; ++ *re += n; ++ } ++ } ++ else ++ nl = memchr (*cp, '\n', *re - *cp); ++ ++ res = *cp; ++ } ++ ++ if (nl == NULL) ++ nl = *re - 1; ++ } ++ ++ *cp = nl + 1; ++ assert (*cp <= *re); ++ ++ return res == *re ? NULL : res; ++} ++ + + int +-__get_nprocs_sched (void) ++__get_nprocs (void) + { +- return __get_nprocs (); ++ enum { buffer_size = 1024 }; ++ char buffer[buffer_size]; ++ char *buffer_end = buffer + buffer_size; ++ char *cp = buffer_end; ++ char *re = buffer_end; ++ ++ const int flags = O_RDONLY | O_CLOEXEC; ++ /* This file contains comma-separated ranges. */ ++ int fd = __open_nocancel ("/sys/devices/system/cpu/online", flags); ++ char *l; ++ int result = 0; ++ if (fd != -1) ++ { ++ l = next_line (fd, buffer, &cp, &re, buffer_end); ++ if (l != NULL) ++ do ++ { ++ char *endp; ++ unsigned long int n = strtoul (l, &endp, 10); ++ if (l == endp) ++ { ++ result = 0; ++ break; ++ } ++ ++ unsigned long int m = n; ++ if (*endp == '-') ++ { ++ l = endp + 1; ++ m = strtoul (l, &endp, 10); ++ if (l == endp) ++ { ++ result = 0; ++ break; ++ } ++ } ++ ++ result += m - n + 1; ++ ++ l = endp; ++ if (l < re && *l == ',') ++ ++l; ++ } ++ while (l < re && *l != '\n'); ++ ++ __close_nocancel_nostatus (fd); ++ ++ if (result > 0) ++ return result; ++ } ++ ++ cp = buffer_end; ++ re = buffer_end; ++ ++ /* Default to an SMP system in case we cannot obtain an accurate ++ number. */ ++ result = 2; ++ ++ fd = __open_nocancel ("/proc/stat", flags); ++ if (fd != -1) ++ { ++ result = 0; ++ ++ while ((l = next_line (fd, buffer, &cp, &re, buffer_end)) != NULL) ++ /* The current format of /proc/stat has all the cpu* entries ++ at the front. We assume here that stays this way. */ ++ if (strncmp (l, "cpu", 3) != 0) ++ break; ++ else if (isdigit (l[3])) ++ ++result; ++ ++ __close_nocancel_nostatus (fd); ++ } ++ ++ return result; + } ++libc_hidden_def (__get_nprocs) ++weak_alias (__get_nprocs, get_nprocs) + + + /* On some architectures it is possible to distinguish between configured +-- +1.8.3.1 + |