From 2a36ab717e8fe678d98f81c14a0b124712719840 Mon Sep 17 00:00:00 2001 From: Peter Oskolkov Date: Wed, 23 Sep 2020 16:36:16 -0700 Subject: rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ This patchset is based on Google-internal RSEQ work done by Paul Turner and Andrew Hunter. When working with per-CPU RSEQ-based memory allocations, it is sometimes important to make sure that a global memory location is no longer accessed from RSEQ critical sections. For example, there can be two per-CPU lists, one is "active" and accessed per-CPU, while another one is inactive and worked on asynchronously "off CPU" (e.g. garbage collection is performed). Then at some point the two lists are swapped, and a fast RCU-like mechanism is required to make sure that the previously active list is no longer accessed. This patch introduces such a mechanism: in short, membarrier() syscall issues an IPI to a CPU, restarting a potentially active RSEQ critical section on the CPU. Signed-off-by: Peter Oskolkov Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mathieu Desnoyers Link: https://lkml.kernel.org/r/20200923233618.2572849-1-posk@google.com --- include/linux/syscalls.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/syscalls.h') diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 75ac7f8ae93c..06db09875aa4 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -974,7 +974,7 @@ asmlinkage long sys_execveat(int dfd, const char __user *filename, const char __user *const __user *argv, const char __user *const __user *envp, int flags); asmlinkage long sys_userfaultfd(int flags); -asmlinkage long sys_membarrier(int cmd, int flags); +asmlinkage long sys_membarrier(int cmd, unsigned int flags, int cpu_id); asmlinkage long sys_mlock2(unsigned long start, size_t len, int flags); asmlinkage long sys_copy_file_range(int fd_in, loff_t __user *off_in, int fd_out, loff_t __user *off_out, -- cgit v1.2.3-59-g8ed1b