diff options
| author | Bodo Stroesser <bstroesser@fujitsu-siemens.com> | 2005-05-06 21:30:54 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-05-06 22:09:30 -0700 |
| commit | 0f7e663dea7f0e22f3b2d07156c5e9d2e8656610 (patch) | |
| tree | 669450b10e1677d3ea65aa7695a7834f791ce329 /arch/um/kernel/tt | |
| parent | b8bd0220c1ac6273eda66e25d992654219f846b6 (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.h | 1 | ||||
| -rw-r--r-- | arch/um/kernel/tt/process_kern.c | 20 |
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, 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) |