From: Anton Ivanov <antiv...@cisco.com>
The reverse case of this race (you must msync before read) is
well known. This is the not so common one.
It can be triggered only on systems which do a lot of task
switching and only at UML startup. If you are starting 200+ UMLs
~ 0.5% will always die without this fix.
Signed-off-by: Anton Ivanov <antiv...@cisco.com>
---
arch/um/include/shared/os.h | 1 +
arch/um/kernel/physmem.c | 1 +
arch/um/os-Linux/file.c | 6 ++++++
3 files changed, 8 insertions(+)
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 89b686c1..3c9738d 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -136,6 +136,7 @@ extern int os_ioctl_generic(int fd, unsigned int cmd,
unsigned long arg);
extern int os_get_ifname(int fd, char *namebuf);
extern int os_set_slip(int fd);
extern int os_mode_fd(int fd, int mode);
+extern int os_fsync_file(int fd);
extern int os_seek_file(int fd, unsigned long long offset);
extern int os_open_file(const char *file, struct openflags flags, int mode);
diff --git a/arch/um/kernel/physmem.c b/arch/um/kernel/physmem.c
index f116db1..30fdd5d0 100644
--- a/arch/um/kernel/physmem.c
+++ b/arch/um/kernel/physmem.c
@@ -103,6 +103,7 @@ void __init setup_physmem(unsigned long start, unsigned
long reserve_end,
*/
os_seek_file(physmem_fd, __pa(&__syscall_stub_start));
os_write_file(physmem_fd, &__syscall_stub_start, PAGE_SIZE);
+ os_fsync_file(physmem_fd);
bootmap_size = init_bootmem(pfn, pfn + delta);
free_bootmem(__pa(reserve_end) + bootmap_size,
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index b049a63..c879b12 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -237,6 +237,12 @@ void os_close_file(int fd)
{
close(fd);
}
+int os_fsync_file(int fd)
+{
+ if (fsync(fd) < 0)
+ return -errno
+ return 0;
+}
int os_seek_file(int fd, unsigned long long offset)
{
--
1.7.10.4
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