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authorBodo Stroesser <bstroesser@fujitsu-siemens.com>2005-05-06 21:30:54 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-06 22:09:30 -0700
commit0f7e663dea7f0e22f3b2d07156c5e9d2e8656610 (patch)
tree669450b10e1677d3ea65aa7695a7834f791ce329 /arch
parent[PATCH] uml: S390 preparation, arch_align_stack (diff)
downloadlinux-dev-0f7e663dea7f0e22f3b2d07156c5e9d2e8656610.tar.xz
linux-dev-0f7e663dea7f0e22f3b2d07156c5e9d2e8656610.zip
[PATCH] uml: Fix process exit race
tt-mode closes switch_pipes in exit_thread_tt and kills processes in switch_to_tt, if the exit_state is EXIT_DEAD or EXIT_ZOMBIE. In very rare cases the exiting process can be scheduled out after having set exit_state and closed switch_pipes (from release_task it calls proc_pid_flush, which might sleep). If this process is to be restarted, UML failes in switch_to_tt with: write of switch_pipe failed, err = 9 We fix this by closing switch_pipes not in exit_thread_tt, but later in release_thread_tt. Additionally, we set switch_pipe[0] = 0 after closing. switch_to_tt must not kill "from" process depending on its exit_state, but must kill it after release_thread was processed only, so it examines switch_pipe[0] for its decision. Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com> Signed-off-by: Jeff Dike <jdike@addtoit.com> Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/um/kernel/process_kern.c1
-rw-r--r--arch/um/kernel/skas/include/mode_kern-skas.h1
-rw-r--r--arch/um/kernel/skas/process_kern.c4
-rw-r--r--arch/um/kernel/tt/include/mode_kern-tt.h1
-rw-r--r--arch/um/kernel/tt/process_kern.c20
5 files changed, 11 insertions, 16 deletions
diff --git a/arch/um/kernel/process_kern.c b/arch/um/kernel/process_kern.c
index 3dcb080c44a0..c1adf7ba3fd1 100644
--- a/arch/um/kernel/process_kern.c
+++ b/arch/um/kernel/process_kern.c
@@ -142,7 +142,6 @@ void release_thread(struct task_struct *task)
void exit_thread(void)
{
- CHOOSE_MODE(exit_thread_tt(), exit_thread_skas());
unprotect_stack((unsigned long) current_thread);
}
diff --git a/arch/um/kernel/skas/include/mode_kern-skas.h b/arch/um/kernel/skas/include/mode_kern-skas.h
index 94c564962378..e48490028111 100644
--- a/arch/um/kernel/skas/include/mode_kern-skas.h
+++ b/arch/um/kernel/skas/include/mode_kern-skas.h
@@ -18,7 +18,6 @@ extern int copy_thread_skas(int nr, unsigned long clone_flags,
unsigned long sp, unsigned long stack_top,
struct task_struct *p, struct pt_regs *regs);
extern void release_thread_skas(struct task_struct *task);
-extern void exit_thread_skas(void);
extern void initial_thread_cb_skas(void (*proc)(void *), void *arg);
extern void init_idle_skas(void);
extern void flush_tlb_kernel_range_skas(unsigned long start,
diff --git a/arch/um/kernel/skas/process_kern.c b/arch/um/kernel/skas/process_kern.c
index 5d096ea63b97..ab5d3271da0b 100644
--- a/arch/um/kernel/skas/process_kern.c
+++ b/arch/um/kernel/skas/process_kern.c
@@ -83,10 +83,6 @@ void release_thread_skas(struct task_struct *task)
{
}
-void exit_thread_skas(void)
-{
-}
-
void fork_handler(int sig)
{
change_sig(SIGUSR1, 1);
diff --git a/arch/um/kernel/tt/include/mode_kern-tt.h b/arch/um/kernel/tt/include/mode_kern-tt.h
index 28aaab3448fa..e0ca0e0b2516 100644
--- a/arch/um/kernel/tt/include/mode_kern-tt.h
+++ b/arch/um/kernel/tt/include/mode_kern-tt.h
@@ -19,7 +19,6 @@ extern int copy_thread_tt(int nr, unsigned long clone_flags, unsigned long sp,
unsigned long stack_top, struct task_struct *p,
struct pt_regs *regs);
extern void release_thread_tt(struct task_struct *task);
-extern void exit_thread_tt(void);
extern void initial_thread_cb_tt(void (*proc)(void *), void *arg);
extern void init_idle_tt(void);
extern void flush_tlb_kernel_range_tt(unsigned long start, unsigned long end);
diff --git a/arch/um/kernel/tt/process_kern.c b/arch/um/kernel/tt/process_kern.c
index f19f7c18febe..df810ca8fc12 100644
--- a/arch/um/kernel/tt/process_kern.c
+++ b/arch/um/kernel/tt/process_kern.c
@@ -65,8 +65,7 @@ void *switch_to_tt(void *prev, void *next, void *last)
panic("write of switch_pipe failed, err = %d", -err);
reading = 1;
- if((from->exit_state == EXIT_ZOMBIE) ||
- (from->exit_state == EXIT_DEAD))
+ if(from->thread.mode.tt.switch_pipe[0] == -1)
os_kill_process(os_getpid(), 0);
err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
@@ -81,8 +80,7 @@ void *switch_to_tt(void *prev, void *next, void *last)
* in case it has not already killed itself.
*/
prev_sched = current->thread.prev_sched;
- if((prev_sched->exit_state == EXIT_ZOMBIE) ||
- (prev_sched->exit_state == EXIT_DEAD))
+ if(prev_sched->thread.mode.tt.switch_pipe[0] == -1)
os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);
change_sig(SIGVTALRM, vtalrm);
@@ -101,14 +99,18 @@ void release_thread_tt(struct task_struct *task)
{
int pid = task->thread.mode.tt.extern_pid;
+ /*
+ * We first have to kill the other process, before
+ * closing its switch_pipe. Else it might wake up
+ * and receive "EOF" before we could kill it.
+ */
if(os_getpid() != pid)
os_kill_process(pid, 0);
-}
-void exit_thread_tt(void)
-{
- os_close_file(current->thread.mode.tt.switch_pipe[0]);
- os_close_file(current->thread.mode.tt.switch_pipe[1]);
+ os_close_file(task->thread.mode.tt.switch_pipe[0]);
+ os_close_file(task->thread.mode.tt.switch_pipe[1]);
+ /* use switch_pipe as flag: thread is released */
+ task->thread.mode.tt.switch_pipe[0] = -1;
}
void suspend_new_thread(int fd)