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authorStanislaw Gruszka <stf_xl@wp.pl>2007-12-18 03:19:46 +0300
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-12-18 06:28:15 +0300
commit4dbed85a35ed37d9608f4f32e5d69efa775d6223 (patch)
tree67ab558db8ccaf8d706a25e5ce87b78be241cffb /arch/um/os-Linux/skas/process.c
parent5867a78f41f84e5388448da62c183255dc22601f (diff)
downloadlinux-4dbed85a35ed37d9608f4f32e5d69efa775d6223.tar.xz
uml: stop gdb from deleting breakpoints when running UML
Sometimes when UML is debugged gdb miss breakpoints. When process traced by gdb do fork, debugger remove breakpoints from child address space. There is possibility to trace more than one fork, but this not work with UML, I guess (only guess) there is a deadlock - gdb waits for UML and UML waits for gdb. When clone() is called with SIGCHLD and CLONE_VM flags, gdb see this as PTRACE_EVENT_FORK not as PTRACE_EVENT_CLONE and remove breakpoints from child and at the same time from traced process, because either have the same address space. Maybe it is possible to do fix in gdb, but I'm not sure if there is easy way to find out if traced and child processes share memory. So I do fix for UML, it simply do not call clone() with both SIGCHLD and CLONE_VM flags together. Additionally __WALL flag is used for waitpid() to assure not miss clone and normal process events. [ jdike - checkpatch fixes ] Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl> Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/um/os-Linux/skas/process.c')
-rw-r--r--arch/um/os-Linux/skas/process.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index d77c81d7068a..e8b7a97e83d3 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -64,7 +64,7 @@ void wait_stub_done(int pid)
int n, status, err;
while (1) {
- CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
+ CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
if ((n < 0) || !WIFSTOPPED(status))
goto bad_wait;
@@ -153,7 +153,7 @@ static void handle_trap(int pid, struct uml_pt_regs *regs,
panic("handle_trap - continuing to end of syscall "
"failed, errno = %d\n", errno);
- CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
+ CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
if ((err < 0) || !WIFSTOPPED(status) ||
(WSTOPSIG(status) != SIGTRAP + 0x80)) {
err = ptrace_dump_regs(pid);
@@ -255,16 +255,18 @@ int start_userspace(unsigned long stub_stack)
panic("start_userspace : mmap failed, errno = %d", errno);
sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
- flags = CLONE_FILES | SIGCHLD;
+ flags = CLONE_FILES;
if (proc_mm)
flags |= CLONE_VM;
+ else
+ flags |= SIGCHLD;
pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
if (pid < 0)
panic("start_userspace : clone failed, errno = %d", errno);
do {
- CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
+ CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
if (n < 0)
panic("start_userspace : wait failed, errno = %d",
errno);
@@ -314,7 +316,7 @@ void userspace(struct uml_pt_regs *regs)
"pid=%d, ptrace operation = %d, errno = %d\n",
pid, op, errno);
- CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
+ CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
if (err < 0)
panic("userspace - waitpid failed, errno = %d\n",
errno);