Linus Torvalds wrote:
> I'm convinced. However, I still want som elargely cosmetic changes to the
> patch, Ingo:
> [...]
I'm not Ingo but changing the patch seemed easy enough to do, even for
me. I append the patch below. It is not meant for inclusion since
there is onw more problem to solve. Ingo patch had another bug. The
user_tid field in the child didn't get set if CLONE_CHILD_CLEARTID was
set. This obviously has bad results.
I've changed the test to read
+ if (clone_flags & (CLONE_CHILD_SETTID|CLONE_CHILD_CLEARTID))
which works for me. But since in schedule_tail() the code reads
+ if (current->user_tid)
+ put_user(current->pid, current->user_tid);
this enables writing the TID even if CLONE_CHILD_SETTID isn't set. The
question is: how to access the clone flag information in the child?
Anyway, since this distinction isn't important for my tests I've applied
the attached patch and all runs fine.
-- --------------. ,-. 444 Castro Street Ulrich Drepper \ ,-----------------' \ Mountain View, CA 94041 USA Red Hat `--' drepper at redhat.com `---------------------------
--- linux-2.5/arch/i386/kernel/entry.S.tid 2002-11-17 16:11:26.000000000 -0800 +++ linux-2.5/arch/i386/kernel/entry.S 2002-11-17 21:56:18.000000000 -0800 @@ -193,10 +193,8 @@ ENTRY(ret_from_fork) -#if CONFIG_SMP || CONFIG_PREEMPT # NOTE: this function takes a parameter but it's unused on x86. call schedule_tail -#endif GET_THREAD_INFO(%ebx) jmp syscall_exit --- linux-2.5/include/linux/sched.h.tid 2002-11-17 16:11:26.000000000 -0800 +++ linux-2.5/include/linux/sched.h 2002-11-17 22:04:56.000000000 -0800 @@ -46,10 +46,11 @@ #define CLONE_NEWNS 0x00020000 /* New namespace group? */ #define CLONE_SYSVSEM 0x00040000 /* share system V SEM_UNDO semantics */ #define CLONE_SETTLS 0x00080000 /* create a new TLS for the child */ -#define CLONE_SETTID 0x00100000 /* write the TID back to userspace */ -#define CLONE_CLEARTID 0x00200000 /* clear the userspace TID */ +#define CLONE_PARENT_SETTID 0x00100000 /* write the TID back to userspace */ +#define CLONE_CHILD_CLEARTID 0x00200000 /* clear the userspace TID */ #define CLONE_DETACHED 0x00400000 /* parent wants no child-exit signal */ #define CLONE_UNTRACED 0x00800000 /* set if the tracing process can't force CLONE_PTRACE on this clone */ +#define CLONE_CHILD_SETTID 0x01000000 /* set the TID in the child */ /* * List of flags we want to share for kernel threads, @@ -332,7 +333,7 @@ wait_queue_head_t wait_chldexit; /* for wait4() */ struct completion *vfork_done; /* for vfork() */ - int *user_tid; /* for CLONE_CLEARTID */ + int *user_tid; /* for CLONE_[SET|CLEAR]TID */ unsigned long rt_priority; unsigned long it_real_value, it_prof_value, it_virt_value; --- linux-2.5/kernel/sched.c.tid 2002-11-17 16:11:26.000000000 -0800 +++ linux-2.5/kernel/sched.c 2002-11-17 21:59:58.000000000 -0800 @@ -503,12 +503,17 @@ * schedule_tail - first thing a freshly forked thread must call. * @prev: the thread we just switched away from. */ -#if CONFIG_SMP || CONFIG_PREEMPT +asmlinkage void FASTCALL(schedule_tail(task_t *prev)); asmlinkage void schedule_tail(task_t *prev) { finish_arch_switch(this_rq(), prev); + + /* + * Does the child thread/process want to be notified of the TID/PID? + */ + if (current->user_tid) + put_user(current->pid, current->user_tid); } -#endif /* * context_switch - switch to the new MM and the new --- linux-2.5/kernel/fork.c.tid 2002-11-17 16:11:26.000000000 -0800 +++ linux-2.5/kernel/fork.c 2002-11-17 22:06:00.000000000 -0800 @@ -822,18 +822,15 @@ retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); if (retval) goto bad_fork_cleanup_namespace; - /* - * Notify the child of the TID? - */ retval = -EFAULT; - if (clone_flags & CLONE_SETTID) + if (clone_flags & CLONE_PARENT_SETTID) if (put_user(p->pid, user_tid)) goto bad_fork_cleanup_namespace; - /* - * Does the userspace VM want the TID cleared on mm_release()? + * Does the userspace VM want the TID set in the child's + * address space and it cleared on mm_release()? */ - if (clone_flags & CLONE_CLEARTID) + if (clone_flags & (CLONE_CHILD_SETTID|CLONE_CHILD_CLEARTID)) p->user_tid = user_tid; /*
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This archive was generated by hypermail 2b29 : Sat Nov 23 2002 - 22:00:20 EST