Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding
Josh Poimboeuf <[email protected]>
| Newsgroups | org.kernel.vger.linux-toolchains,org.kernel.vger.linux-kernel,org.kernel.vger.linux-perf-users |
|---|---|
| Message-ID | <[email protected]> |
On Tue, Oct 29, 2024 at 02:27:09PM +0100, Peter Zijlstra wrote:
> > +int sframe_add_section(unsigned long sframe_addr, unsigned long text_start,
> > + unsigned long text_end)
> > +{
> > + struct mm_struct *mm = current->mm;
> > + struct vm_area_struct *sframe_vma;
> > +
> > + mmap_read_lock(mm);
>
> DEFINE_GUARD(mmap_read_lock, struct mm_struct *,
> mmap_read_lock(_T), mmap_read_unlock(_T))
>
> in include/linux/mmap_lock.h ?
Will do.
> > @@ -2784,6 +2785,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> > case PR_RISCV_SET_ICACHE_FLUSH_CTX:
> > error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3);
> > break;
> > + case PR_ADD_SFRAME:
> > + if (arg5)
> > + return -EINVAL;
> > + error = sframe_add_section(arg2, arg3, arg4);
> > + break;
> > + case PR_REMOVE_SFRAME:
> > + if (arg3 || arg4 || arg5)
> > + return -EINVAL;
> > + error = sframe_remove_section(arg2);
> > + break;
> > default:
> > error = -EINVAL;
> > break;
>
> So I realize that mtree has an internal lock, but are we sure we don't
> want a lock around those prctl()s?
Not that I can tell? It relies on the mtree internal locking for
atomicity.
For sframe_remove_section() it uses srcu to delay the freeing until all
sframe_find()'s have completed.
--
Josh