On Fri, Mar 31, 2023 at 05:06:17AM +0100, Matthew Wilcox wrote:
> On Thu, Mar 30, 2023 at 08:45:52PM -0700, Luis Chamberlain wrote:
> > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> > index 291d4167fab8..00c9fcd90e1a 100644
> > --- a/arch/x86/kernel/cpu/intel.c
> > +++ b/arch/x86/kernel/cpu/intel.c
> > @@ -1177,7 +1177,7 @@ static const struct {
> > static struct ratelimit_state bld_ratelimit;
> >
> > static unsigned int sysctl_sld_mitigate = 1;
> > -static DEFINE_SEMAPHORE(buslock_sem);
> > +static DEFINE_MUTEX(buslock_sem);
> >
> > #ifdef CONFIG_PROC_SYSCTL
> > static struct ctl_table sld_sysctls[] = {
> > @@ -1315,7 +1315,7 @@ static void split_lock_init(void)
> > static void __split_lock_reenable_unlock(struct work_struct *work)
> > {
> > sld_update_msr(true);
> > - up(&buslock_sem);
> > + mutex_unlock(&buslock_sem);
> > }
> >
> > static DECLARE_DELAYED_WORK(sl_reenable_unlock, __split_lock_reenable_unlock);
>
> ^^^ clearly unsafe. __split_lock_reenable_unlock() is called as a
> delayed_work(), ie not in the context of the mutex locker. lockdep
> will freak out at this.
>
> > @@ -351,12 +351,12 @@ virt_efi_set_variable_nonblocking(efi_char16_t *name, efi_guid_t *vendor,
> > {
> > efi_status_t status;
> >
> > - if (down_trylock(&efi_runtime_lock))
> > + if (!mutex_trylock(&efi_runtime_lock))
> > return EFI_NOT_READY;
>
> looks to me like this can be called while we're oopsing. if that's in
> non-process context, lockdep will get angry.
>
> > @@ -149,10 +149,10 @@ EXPORT_SYMBOL_NS_GPL(efivar_lock, EFIVAR);
> > */
> > int efivar_trylock(void)
> > {
> > - if (down_trylock(&efivars_lock))
> > + if (!mutex_trylock(&efivars_lock))
>
> also can be called from oops context.
>
> > @@ -228,7 +228,7 @@ adb_probe_task(void *x)
> > do_adb_reset_bus();
> > pr_debug("adb: finished probe task...\n");
> >
> > - up(&adb_probe_mutex);
> > + mutex_unlock(&adb_probe_mutex);
>
> adb_probe_task() can be called from a different context than the lock
> holder.
>
> > @@ -10594,7 +10594,7 @@ static bool bnx2x_prev_is_path_marked(struct bnx2x *bp)
> > struct bnx2x_prev_path_list *tmp_list;
> > bool rc = false;
> >
> > - if (down_trylock(&bnx2x_prev_sem))
> > + if (!mutex_trylock(&bnx2x_prev_sem))
>
> bet you this can be called from interrupt context.
>
> this really isn't something to use coccinelle for.
Coccinelle gives you what *would* happen, its up to us to review
if the conversion is correct. Thanks for the feedback, seems like
we're not going there for some users, contrary to what we expected.
Luis
