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| author | Florian Weimer <fweimer@redhat.com> | 2024-03-15 19:08:24 +0100 |
|---|---|---|
| committer | Arjun Shankar <arjun@redhat.com> | 2024-03-18 11:28:19 +0100 |
| commit | 71fcdba577884627c3ee4e43beb915da752efb1f (patch) | |
| tree | 751f97b1a0fbde01104d55e8ec1d603808629017 /sysdeps | |
| parent | 1b9c1a0047fb26a65a9b2a7b8cd977243f7d353c (diff) | |
| download | glibc-71fcdba577884627c3ee4e43beb915da752efb1f.zip glibc-71fcdba577884627c3ee4e43beb915da752efb1f.tar.gz glibc-71fcdba577884627c3ee4e43beb915da752efb1f.tar.bz2 | |
linux: Use rseq area unconditionally in sched_getcpu (bug 31479)
Originally, nptl/descr.h included <sys/rseq.h>, but we removed that
in commit 2c6b4b272e6b4d07303af25709051c3e96288f2d ("nptl:
Unconditionally use a 32-byte rseq area"). After that, it was
not ensured that the RSEQ_SIG macro was defined during sched_getcpu.c
compilation that provided a definition. This commit always checks
the rseq area for CPU number information before using the other
approaches.
This adds an unnecessary (but well-predictable) branch on
architectures which do not define RSEQ_SIG, but its cost is small
compared to the system call. Most architectures that have vDSO
acceleration for getcpu also have rseq support.
Fixes: 2c6b4b272e6b4d07303af25709051c3e96288f2d
Fixes: 1d350aa06091211863e41169729cee1bca39f72f
Reviewed-by: Arjun Shankar <arjun@redhat.com>
(cherry picked from commit 7a76f218677d149d8b7875b336722108239f7ee9)
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/unix/sysv/linux/sched_getcpu.c | 8 |
1 files changed, 0 insertions, 8 deletions
diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c index dfb8845..72a3360 100644 --- a/sysdeps/unix/sysv/linux/sched_getcpu.c +++ b/sysdeps/unix/sysv/linux/sched_getcpu.c @@ -33,17 +33,9 @@ vsyscall_sched_getcpu (void) return r == -1 ? r : cpu; } -#ifdef RSEQ_SIG int sched_getcpu (void) { int cpu_id = THREAD_GETMEM_VOLATILE (THREAD_SELF, rseq_area.cpu_id); return __glibc_likely (cpu_id >= 0) ? cpu_id : vsyscall_sched_getcpu (); } -#else /* RSEQ_SIG */ -int -sched_getcpu (void) -{ - return vsyscall_sched_getcpu (); -} -#endif /* RSEQ_SIG */ |