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Andrew Morton wrote:
>It would be possible, yes.
>
>But thread creation is a "rare" event compared to pagefaults and syscalls.
>An atomic_t will be OK there.
>
>
Actually, the code is correct. The documentation it bogus. lock_kernel()
never achieved any protection: the copy_xy() functions can sleep.
What about the attached docu update?
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Manfred
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filename="patch-nrthreads"
--- 2.5/kernel/fork.c 2003-04-20 11:19:14.000000000 +0200
+++ build-2.5/kernel/fork.c 2003-04-21 20:44:37.000000000 +0200
@@ -43,7 +43,9 @@
extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
extern void exit_semundo(struct task_struct *tsk);
-/* The idle threads do not count.. */
+/* The idle threads do not count..
+ * Protected by write_lock_irq(&tasklist_lock)
+ */
int nr_threads;
int max_threads;
@@ -792,9 +794,9 @@
atomic_inc(&p->user->processes);
/*
- * Counter increases are protected by
- * the kernel lock so nr_threads can't
- * increase under us (but it may decrease).
+ * If multiple threads are within copy_process(), then this check
+ * triggers too late. This doesn't hurt, the check is only there
+ * to stop root fork bombs.
*/
if (nr_threads >= max_threads)
goto bad_fork_cleanup_count;
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