Hi, In August 2019 I tried to unlock lseek(2) which failed since the vnode lock could not be acquired without holding the kernel lock back then, found the hard way. claudio@ recently[1] make it possible to acquire a vnode lock without holding the kernel lock. I therefore would like to give this another try. The kernel lock is still required around VOP_GETATTR() as the underlying file system implementations are not yet^W MP-safe.
Comments? OK? [1] https://github.com/openbsd/src/commit/9d6122f62b6ed32d6c956e1d5269114b2f24ea14 Index: kern/syscalls.master =================================================================== RCS file: /cvs/src/sys/kern/syscalls.master,v retrieving revision 1.209 diff -u -p -r1.209 syscalls.master --- kern/syscalls.master 18 Mar 2021 08:43:38 -0000 1.209 +++ kern/syscalls.master 29 Apr 2021 19:09:58 -0000 @@ -349,7 +349,7 @@ 197 STD { void *sys_mmap(void *addr, size_t len, int prot, \ int flags, int fd, long pad, off_t pos); } 198 INDIR { quad_t sys___syscall(quad_t num, ...); } -199 STD { off_t sys_lseek(int fd, int pad, off_t offset, \ +199 STD NOLOCK { off_t sys_lseek(int fd, int pad, off_t offset, \ int whence); } 200 STD { int sys_truncate(const char *path, int pad, \ off_t length); } Index: kern/vfs_vnops.c =================================================================== RCS file: /cvs/src/sys/kern/vfs_vnops.c,v retrieving revision 1.115 diff -u -p -r1.115 vfs_vnops.c --- kern/vfs_vnops.c 28 Apr 2021 09:53:53 -0000 1.115 +++ kern/vfs_vnops.c 29 Apr 2021 19:09:58 -0000 @@ -657,7 +657,9 @@ vn_seek(struct file *fp, off_t *offset, newoff = fp->f_offset + *offset; break; case SEEK_END: + KERNEL_LOCK(); error = VOP_GETATTR(vp, &vattr, cred, p); + KERNEL_UNLOCK(); if (error) goto out; newoff = *offset + (off_t)vattr.va_size;
