On Tue, Sep 08, 2020 at 01:45:20PM +0200, [email protected] wrote: > On Fri, Sep 04, 2020 at 05:32:30PM +0200, Ahmed S. Darwish wrote: > > @@ -406,13 +443,20 @@ static inline int read_seqcount_t_retry(const > > seqcount_t *s, unsigned start) > > return __read_seqcount_t_retry(s, start); > > } > > > > +/* > > + * Enforce non-preemptibility for all seqcount_LOCKNAME_t writers. Don't > > + * do it for PREEMPT_RT, for the reasons outlined at __SEQ_LOCK(). > > + */ > > +#define __seq_enforce_writer_non_preemptibility(s) \ > > + (!IS_ENABLED(CONFIG_PREEMPT_RT) && __seqcount_lock_preemptible(s)) > > + > > /** > > * raw_write_seqcount_begin() - start a seqcount_t write section w/o > > lockdep > > * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants > > */ > > #define raw_write_seqcount_begin(s) > > \ > > do { > > \ > > - if (__seqcount_lock_preemptible(s)) \ > > + if (__seq_enforce_writer_non_preemptibility(s)) \ > > preempt_disable(); \ > > \ > > raw_write_seqcount_t_begin(__seqcount_ptr(s)); \ > > @@ -433,7 +477,7 @@ static inline void > > raw_write_seqcount_t_begin(seqcount_t *s) > > do { > > \ > > raw_write_seqcount_t_end(__seqcount_ptr(s)); \ > > \ > > - if (__seqcount_lock_preemptible(s)) \ > > + if (__seq_enforce_writer_non_preemptibility(s)) \ > > preempt_enable(); \ > > } while (0) > > > > @@ -456,7 +500,7 @@ static inline void raw_write_seqcount_t_end(seqcount_t > > *s) > > do { > > \ > > __seqcount_assert_lock_held(s); \ > > \ > > - if (__seqcount_lock_preemptible(s)) \ > > + if (__seq_enforce_writer_non_preemptibility(s)) \ > > preempt_disable(); \ > > \ > > write_seqcount_t_begin_nested(__seqcount_ptr(s), subclass); \ > > @@ -483,7 +527,7 @@ static inline void > > write_seqcount_t_begin_nested(seqcount_t *s, int subclass) > > do { > > \ > > __seqcount_assert_lock_held(s); \ > > \ > > - if (__seqcount_lock_preemptible(s)) \ > > + if (__seq_enforce_writer_non_preemptibility(s)) \ > > preempt_disable(); \ > > \ > > write_seqcount_t_begin(__seqcount_ptr(s)); \ > > @@ -504,7 +548,7 @@ static inline void write_seqcount_t_begin(seqcount_t *s) > > do { > > \ > > write_seqcount_t_end(__seqcount_ptr(s)); \ > > \ > > - if (__seqcount_lock_preemptible(s)) \ > > + if (__seq_enforce_writer_non_preemptibility(s)) \ > > preempt_enable(); \ > > } while (0) > > I've replaced the above with the below, afaict there were no users of > __seqcount_lock_preemptible() left. > > --- a/include/linux/seqlock.h > +++ b/include/linux/seqlock.h > @@ -228,7 +228,11 @@ __seqprop_##lockname##_sequence(const se > static __always_inline bool \ > __seqprop_##lockname##_preemptible(const seqcount_##lockname##_t *s) \ > { \ > - return preemptible; \ > + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) \ > + return preemptible; \ > + \ > + /* PREEMPT_RT relies on the above LOCK+UNLOCK */ \ > + return false; \ > } \ > \
Sounds good.
