On Wed, Apr 19, 2017 at 04:25:03PM +0200, Peter Zijlstra wrote:
> On Tue, Mar 14, 2017 at 05:18:52PM +0900, Byungchul Park wrote:
> > +struct hist_lock {
> > + /*
> > + * Each work of workqueue might run in a different context,
> > + * thanks to concurrency support of workqueue. So we have to
> > + * distinguish each work to avoid false positive.
> > + */
> > + unsigned int work_id;
> > };
>
> > @@ -1749,6 +1749,14 @@ struct task_struct {
> > struct held_lock held_locks[MAX_LOCK_DEPTH];
> > gfp_t lockdep_reclaim_gfp;
> > #endif
> > +#ifdef CONFIG_LOCKDEP_CROSSRELEASE
> > +#define MAX_XHLOCKS_NR 64UL
> > + struct hist_lock *xhlocks; /* Crossrelease history locks */
> > + unsigned int xhlock_idx;
> > + unsigned int xhlock_idx_soft; /* For backing up at softirq entry */
> > + unsigned int xhlock_idx_hard; /* For backing up at hardirq entry */
> > + unsigned int work_id;
> > +#endif
> > #ifdef CONFIG_UBSAN
> > unsigned int in_ubsan;
> > #endif
>
> > +/*
> > + * Crossrelease needs to distinguish each work of workqueues.
> > + * Caller is supposed to be a worker.
> > + */
> > +void crossrelease_work_start(void)
> > +{
> > + if (current->xhlocks)
> > + current->work_id++;
> > +}
>
> > +/*
> > + * Only access local task's data, so irq disable is only required.
> > + */
> > +static int same_context_xhlock(struct hist_lock *xhlock)
> > +{
> > + struct task_struct *curr = current;
> > +
> > + /* In the case of hardirq context */
> > + if (curr->hardirq_context) {
> > + if (xhlock->hlock.irq_context & 2) /* 2: bitmask for hardirq */
> > + return 1;
> > + /* In the case of softriq context */
> > + } else if (curr->softirq_context) {
> > + if (xhlock->hlock.irq_context & 1) /* 1: bitmask for softirq */
> > + return 1;
> > + /* In the case of process context */
> > + } else {
> > + if (xhlock->work_id == curr->work_id)
> > + return 1;
> > + }
> > + return 0;
> > +}
>
> I still don't like work_id; it doesn't have anything to do with
> workqueues per se, other than the fact that they end up using it.
>
> It's a history generation id; touching it completely invalidates our
> history. Workqueues need this because they run independent work from the
> same context.
>
> But the same is true for other sites. Last time I suggested
> lockdep_assert_empty() to denote all suck places (and note we already
> have lockdep_sys_exit() that hooks into the return to user path).
I'm sorry but I don't understand what you intend. It would be appriciated
if you explain more.
You might know why I introduced the 'work_id'.. Is there any alternative?
Thank you.
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