[PATCH] oom: don't kill current when another OOM in progress
A previous patch to allow an exiting task to OOM kill itself (and thereby avoid a little deadlock) introduced a problem. We don't want the PF_EXITING task, even if it is 'current', to access mem reserves if there is already a TIF_MEMDIE process in the system sucking up reserves. Also make the commenting a little bit clearer, and note that our current scheme of effectively single threading the OOM killer is not itself perfect. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>wifi-calibration
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01017a2270
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b78483a4ba
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@ -215,6 +215,18 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
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if (is_init(p))
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if (is_init(p))
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continue;
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continue;
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/*
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* This task already has access to memory reserves and is
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* being killed. Don't allow any other task access to the
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* memory reserve.
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*
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* Note: this may have a chance of deadlock if it gets
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* blocked waiting for another task which itself is waiting
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* for memory. Is there a better alternative?
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*/
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if (test_tsk_thread_flag(p, TIF_MEMDIE))
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return ERR_PTR(-1UL);
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/*
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/*
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* This is in the process of releasing memory so wait for it
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* This is in the process of releasing memory so wait for it
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* to finish before killing some other task by mistake.
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* to finish before killing some other task by mistake.
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@ -223,16 +235,15 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
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* go ahead if it is exiting: this will simply set TIF_MEMDIE,
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* go ahead if it is exiting: this will simply set TIF_MEMDIE,
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* which will allow it to gain access to memory reserves in
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* which will allow it to gain access to memory reserves in
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* the process of exiting and releasing its resources.
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* the process of exiting and releasing its resources.
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* Otherwise we could get an OOM deadlock.
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* Otherwise we could get an easy OOM deadlock.
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*/
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*/
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if ((p->flags & PF_EXITING) && p == current) {
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if (p->flags & PF_EXITING) {
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if (p != current)
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return ERR_PTR(-1UL);
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chosen = p;
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chosen = p;
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*ppoints = ULONG_MAX;
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*ppoints = ULONG_MAX;
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break;
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}
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}
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if ((p->flags & PF_EXITING) ||
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test_tsk_thread_flag(p, TIF_MEMDIE))
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return ERR_PTR(-1UL);
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if (p->oomkilladj == OOM_DISABLE)
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if (p->oomkilladj == OOM_DISABLE)
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continue;
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continue;
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