* Oleg Nesterov <[email protected]> [2012-12-28 19:13:10]: > filter_chain() was added into install_breakpoint/remove_breakpoint to > simplify the initial changes but this is sub-optimal. > > This patch shifts the callsite to the callers, register_for_each_vma() > and uprobe_mmap(). This way: > > - It will be easier to add the new arguments. This is the main reason, > we can do more optimizations later. > > - register_for_each_vma(is_register => true) can be optimized, we only > need to consult the new consumer. The previous consumers were already > asked when they called uprobe_register(). > > This patch also moves the MMF_HAS_UPROBES check from remove_breakpoint(), > this allows to avoid the potentionally costly filter_chain(). Note that > register_for_each_vma(is_register => false) doesn't really need to take > >consumer_rwsem, but I don't think it makes sense to optimize this and > introduce filter_chain_lockless(). > > Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Srikar Dronamraju <[email protected]> > --- > kernel/events/uprobes.c | 44 +++++++++++++++++++++----------------------- > 1 files changed, 21 insertions(+), 23 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 105ac0d..60b0a90 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -579,6 +579,11 @@ static int prepare_uprobe(struct uprobe *uprobe, struct > file *file, > return ret; > } > > +static inline bool consumer_filter(struct uprobe_consumer *uc) > +{ > + return true; /* TODO: !uc->filter || uc->filter(...) */ > +} > + > static bool filter_chain(struct uprobe *uprobe) > { > struct uprobe_consumer *uc; > @@ -586,8 +591,7 @@ static bool filter_chain(struct uprobe *uprobe) > > down_read(&uprobe->consumer_rwsem); > for (uc = uprobe->consumers; uc; uc = uc->next) { > - /* TODO: ret = uc->filter(...) */ > - ret = true; > + ret = consumer_filter(uc); > if (ret) > break; > } > @@ -603,15 +607,6 @@ install_breakpoint(struct uprobe *uprobe, struct > mm_struct *mm, > bool first_uprobe; > int ret; > > - /* > - * If probe is being deleted, unregister thread could be done with > - * the vma-rmap-walk through. Adding a probe now can be fatal since > - * nobody will be able to cleanup. But in this case filter_chain() > - * must return false, all consumers have gone away. > - */ > - if (!filter_chain(uprobe)) > - return 0; > - > ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr); > if (ret) > return ret; > @@ -636,12 +631,6 @@ install_breakpoint(struct uprobe *uprobe, struct > mm_struct *mm, > static int > remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long > vaddr) > { > - if (!test_bit(MMF_HAS_UPROBES, &mm->flags)) > - return 0; > - > - if (filter_chain(uprobe)) > - return 0; > - > set_bit(MMF_RECALC_UPROBES, &mm->flags); > return set_orig_insn(&uprobe->arch, mm, vaddr); > } > @@ -781,10 +770,14 @@ static int register_for_each_vma(struct uprobe *uprobe, > bool is_register) > vaddr_to_offset(vma, info->vaddr) != uprobe->offset) > goto unlock; > > - if (is_register) > - err = install_breakpoint(uprobe, mm, vma, info->vaddr); > - else > - err |= remove_breakpoint(uprobe, mm, info->vaddr); > + if (is_register) { > + /* consult only the "caller", new consumer. */ > + if (consumer_filter(uprobe->consumers)) > + err = install_breakpoint(uprobe, mm, vma, > info->vaddr); > + } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) { > + if (!filter_chain(uprobe)) > + err |= remove_breakpoint(uprobe, mm, > info->vaddr); > + } > > unlock: > up_write(&mm->mmap_sem); > @@ -968,9 +961,14 @@ int uprobe_mmap(struct vm_area_struct *vma) > > mutex_lock(uprobes_mmap_hash(inode)); > build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list); > - > + /* > + * We can race with uprobe_unregister(), this uprobe can be already > + * removed. But in this case filter_chain() must return false, all > + * consumers have gone away. > + */ > list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) { > - if (!fatal_signal_pending(current)) { > + if (!fatal_signal_pending(current) && > + filter_chain(uprobe)) { > unsigned long vaddr = offset_to_vaddr(vma, > uprobe->offset); > install_breakpoint(uprobe, vma->vm_mm, vma, vaddr); > } > -- > 1.5.5.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
