diff options
Diffstat (limited to 'include/linux/rseq.h')
| -rw-r--r-- | include/linux/rseq.h | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/include/linux/rseq.h b/include/linux/rseq.h index 7f347c3a4af8..92f9cd49489b 100644 --- a/include/linux/rseq.h +++ b/include/linux/rseq.h @@ -5,6 +5,8 @@ #ifdef CONFIG_RSEQ #include <linux/sched.h> +#include <uapi/linux/rseq.h> + void __rseq_handle_notify_resume(struct ksignal *sig, struct pt_regs *regs); static inline void rseq_handle_notify_resume(struct pt_regs *regs) @@ -48,7 +50,7 @@ static inline void rseq_virt_userspace_exit(void) static inline void rseq_reset(struct task_struct *t) { memset(&t->rseq, 0, sizeof(t->rseq)); - t->rseq.ids.cpu_cid = ~0ULL; + t->rseq.ids.cpu_id = RSEQ_CPU_ID_UNINITIALIZED; } static inline void rseq_execve(struct task_struct *t) @@ -59,15 +61,19 @@ static inline void rseq_execve(struct task_struct *t) /* * If parent process has a registered restartable sequences area, the * child inherits. Unregister rseq for a clone with CLONE_VM set. + * + * On fork, keep the IDs (CPU, MMCID) of the parent, which avoids a fault + * on the COW page on exit to user space, when the child stays on the same + * CPU as the parent. That's obviously not guaranteed, but in overcommit + * scenarios it is more likely and optimizes for the fork/exec case without + * taking the fault. */ static inline void rseq_fork(struct task_struct *t, u64 clone_flags) { - if (clone_flags & CLONE_VM) { + if (clone_flags & CLONE_VM) rseq_reset(t); - } else { + else t->rseq = current->rseq; - t->rseq.ids.cpu_cid = ~0ULL; - } } #else /* CONFIG_RSEQ */ |