Messages in this thread | | | Subject | Re: PROBLEM: Bug in __pollwait() can cause select() and poll() to hang in 2.4.21 | From | Andi Kleen <> | Date | 19 Jun 2003 18:42:31 +0200 |
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Ray Bryant <raybry@sgi.com> writes: > > select() and poll() call a common routine: __pollwait(). On the > first call to __pollwait(), it calls __get_free_page(GFP_KERNEL) to > allocate a table to hold wait queues. In the natural course of things, > this calls into __alloc_pages(). In low memory situations, the process > can then end up in the rebalance code at the bottom of __alloc_pages() > where there is a call to yield(). If the process makes this call, this > is a bad thing [tm], since the process state at that point is > TASK_INTERRUPTIBLE. There is no wait queue yet for the process (that is > done later in __pollwait()) and no schedule timeout event has yet been > created (that is done later in select()) so the process will never > return from the call to yield().
Nasty bug. How about adding a BUG() for current->state != TASK_RUNNING at the beginning of __alloc_pages unless GFP_ATOMIC is set?
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