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util: Set util_cpu_caps.num_cpu_mask_bits based on total CPUs in the system

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In the current code, this prevents a very unlikely corner case.  More
importantly, it should prevent the next commit from breaking the
universe.

Imagine a system with 64 CPUs configured, but first 32 CPUs are offline.
_SC_NPROCESSORS_CONF will return 32.  All of the surrounding code will
interpret this as meaning CPUs 0 through 31, but all of those CPUs are
offline.  Nothing good can happen then.

The problem cases require systems with more than 32 CPUs because
util_cpu_caps.num_cpu_mask_bits is always rounded up to a multiple of
32.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11228>
This commit is contained in:
Ian Romanick 2021-06-08 16:36:32 -07:00 • committed by Marge Bot
parent 5623c75e40
commit c12b52b856
1 changed files with 33 additions and 9 deletions
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42
src/util/u_cpu_detect.c
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@ -555,6 +555,9 @@ get_cpu_topology(void)
static void
util_cpu_detect_once(void)
{
int available_cpus = 0;
int total_cpus = 0;
memset(&util_cpu_caps, 0, sizeof util_cpu_caps);
/* Count the number of CPUs in system */
@ -562,7 +565,7 @@ util_cpu_detect_once(void)
{
SYSTEM_INFO system_info;
GetSystemInfo(&system_info);
util_cpu_caps.nr_cpus = MAX2(1, system_info.dwNumberOfProcessors);
available_cpus = MAX2(1, system_info.dwNumberOfProcessors);
}
#elif defined(PIPE_OS_UNIX)
/* Linux, FreeBSD, DragonFly, and Mac OS X should have
@ -576,12 +579,12 @@ util_cpu_detect_once(void)
int len = sizeof(ncpu);
sysctl(mib, 2, &ncpu, &len, NULL, 0);
util_cpu_caps.nr_cpus = ncpu;
available_cpus = ncpu;
}
# elif defined(_SC_NPROCESSORS_ONLN)
util_cpu_caps.nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
if (util_cpu_caps.nr_cpus == ~0)
util_cpu_caps.nr_cpus = 1;
available_cpus = sysconf(_SC_NPROCESSORS_ONLN);
if (available_cpus == ~0)
available_cpus = 1;
# elif defined(PIPE_OS_BSD)
{
const int mib[] = { CTL_HW, HW_NCPU };
@ -589,15 +592,36 @@ util_cpu_detect_once(void)
int len = sizeof(ncpu);
sysctl(mib, 2, &ncpu, &len, NULL, 0);
util_cpu_caps.nr_cpus = ncpu;
available_cpus = ncpu;
}
# endif /* defined(PIPE_OS_BSD) */
/* Determine the maximum number of CPUs configured in the system. This is
* used to properly set num_cpu_mask_bits below. On BSDs that don't have
* HW_NCPUONLINE, it was not clear whether HW_NCPU is the number of
* configured or the number of online CPUs. For that reason, prefer the
* _SC_NPROCESSORS_CONF path on all BSDs.
*/
# if defined(_SC_NPROCESSORS_CONF)
total_cpus = sysconf(_SC_NPROCESSORS_CONF);
if (total_cpus == ~0)
total_cpus = 1;
# elif defined(PIPE_OS_BSD)
{
const int mib[] = { CTL_HW, HW_NCPU };
int ncpu;
int len = sizeof(ncpu);
sysctl(mib, 2, &ncpu, &len, NULL, 0);
total_cpus = ncpu;
}
# endif /* defined(PIPE_OS_BSD) */
#endif /* defined(PIPE_OS_UNIX) */
if (util_cpu_caps.nr_cpus == 0)
util_cpu_caps.nr_cpus = 1;
util_cpu_caps.nr_cpus = MAX2(1, available_cpus);
total_cpus = MAX2(total_cpus, util_cpu_caps.nr_cpus);
util_cpu_caps.num_cpu_mask_bits = align(util_cpu_caps.nr_cpus, 32);
util_cpu_caps.num_cpu_mask_bits = align(total_cpus, 32);
/* Make the fallback cacheline size nonzero so that it can be
* safely passed to align().