diff options
Diffstat (limited to '0002-linux-Use-rseq-area-unconditionally-in-sched_getcpu-.patch')
| -rw-r--r-- | 0002-linux-Use-rseq-area-unconditionally-in-sched_getcpu-.patch | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/0002-linux-Use-rseq-area-unconditionally-in-sched_getcpu-.patch b/0002-linux-Use-rseq-area-unconditionally-in-sched_getcpu-.patch new file mode 100644 index 0000000..b3d890d --- /dev/null +++ b/0002-linux-Use-rseq-area-unconditionally-in-sched_getcpu-.patch @@ -0,0 +1,52 @@ +From 5753cda1ca0749002c4718122a9b6d5177087b7b Mon Sep 17 00:00:00 2001 +From: Florian Weimer <fweimer@redhat.com> +Date: Fri, 15 Mar 2024 19:08:24 +0100 +Subject: [PATCH 02/26] 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) +--- + sysdeps/unix/sysv/linux/sched_getcpu.c | 8 -------- + 1 file changed, 8 deletions(-) + +diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c +index 4457d714bc..22700ef846 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 */ +-- +2.33.0 + |