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authorBodo Stroesser <bstroesser@fujitsu-siemens.com>2005-05-07 00:30:54 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-05-07 01:09:30 -0400
commit0f7e663dea7f0e22f3b2d07156c5e9d2e8656610 (patch)
tree669450b10e1677d3ea65aa7695a7834f791ce329 /arch/um/kernel/tt
parentb8bd0220c1ac6273eda66e25d992654219f846b6 (diff)
[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/um/kernel/tt')
-rw-r--r--arch/um/kernel/tt/include/mode_kern-tt.h1
-rw-r--r--arch/um/kernel/tt/process_kern.c20
2 files changed, 11 insertions, 10 deletions
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,
19 unsigned long stack_top, struct task_struct *p, 19 unsigned long stack_top, struct task_struct *p,
20 struct pt_regs *regs); 20 struct pt_regs *regs);
21extern void release_thread_tt(struct task_struct *task); 21extern void release_thread_tt(struct task_struct *task);
22extern void exit_thread_tt(void);
23extern void initial_thread_cb_tt(void (*proc)(void *), void *arg); 22extern void initial_thread_cb_tt(void (*proc)(void *), void *arg);
24extern void init_idle_tt(void); 23extern void init_idle_tt(void);
25extern void flush_tlb_kernel_range_tt(unsigned long start, unsigned long end); 24extern 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)
65 panic("write of switch_pipe failed, err = %d", -err); 65 panic("write of switch_pipe failed, err = %d", -err);
66 66
67 reading = 1; 67 reading = 1;
68 if((from->exit_state == EXIT_ZOMBIE) || 68 if(from->thread.mode.tt.switch_pipe[0] == -1)
69 (from->exit_state == EXIT_DEAD))
70 os_kill_process(os_getpid(), 0); 69 os_kill_process(os_getpid(), 0);
71 70
72 err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c)); 71 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)
81 * in case it has not already killed itself. 80 * in case it has not already killed itself.
82 */ 81 */
83 prev_sched = current->thread.prev_sched; 82 prev_sched = current->thread.prev_sched;
84 if((prev_sched->exit_state == EXIT_ZOMBIE) || 83 if(prev_sched->thread.mode.tt.switch_pipe[0] == -1)
85 (prev_sched->exit_state == EXIT_DEAD))
86 os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1); 84 os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);
87 85
88 change_sig(SIGVTALRM, vtalrm); 86 change_sig(SIGVTALRM, vtalrm);
@@ -101,14 +99,18 @@ void release_thread_tt(struct task_struct *task)
101{ 99{
102 int pid = task->thread.mode.tt.extern_pid; 100 int pid = task->thread.mode.tt.extern_pid;
103 101
102 /*
103 * We first have to kill the other process, before
104 * closing its switch_pipe. Else it might wake up
105 * and receive "EOF" before we could kill it.
106 */
104 if(os_getpid() != pid) 107 if(os_getpid() != pid)
105 os_kill_process(pid, 0); 108 os_kill_process(pid, 0);
106}
107 109
108void exit_thread_tt(void) 110 os_close_file(task->thread.mode.tt.switch_pipe[0]);
109{ 111 os_close_file(task->thread.mode.tt.switch_pipe[1]);
110 os_close_file(current->thread.mode.tt.switch_pipe[0]); 112 /* use switch_pipe as flag: thread is released */
111 os_close_file(current->thread.mode.tt.switch_pipe[1]); 113 task->thread.mode.tt.switch_pipe[0] = -1;
112} 114}
113 115
114void suspend_new_thread(int fd) 116void suspend_new_thread(int fd)