[[RFC][PATCH RT 6/6] vtime: Convert vtime_seqlock into raw_spinlock_t and seqcount combo] On 26/06/2013 (Wed 15:28) Steven Rostedt wrote:
> The vtime seqlock needs to be taken in true interrupt context on -rt. > The normal seqlocks are converted to mutexes when PREEMPT_RT_FULL is > enabled, which will break the vtime code as the calls are done from > interrupt context. > > Convert the vtime seqlock into the raw_spinlock_t and seqcount combo > that can be done in interrupt context. Alternatively, we could revive the raw seqlock patch from Thomas? https://lkml.org/lkml/2010/2/17/238 Below is a version updating it to 3.8.x-RT. One downside is that current mainline kernels have raw_seqcount_begin() function, which has nothing to do with preempt-rt, so the seqcount function namespace can get confusing unless we rename raw_seqcount_begin to something that doesn't sound RT-ish. Paul. -- diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 939ea1a..5a3f6fd 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -185,6 +185,11 @@ static inline void write_seqcount_barrier(seqcount_t *s) typedef struct { struct seqcount seqcount; + raw_spinlock_t lock; +} raw_seqlock_t; + +typedef struct { + struct seqcount seqcount; spinlock_t lock; } seqlock_t; @@ -192,6 +197,21 @@ typedef struct { * These macros triggered gcc-3.x compile-time problems. We think these are * OK now. Be cautious. */ +#define __RAW_SEQLOCK_UNLOCKED(lockname) \ + { \ + .seqcount = SEQCNT_ZERO, \ + .lock = __RAW_SPIN_LOCK_UNLOCKED(lockname) \ + } + +#define raw_seqlock_init(x) \ + do { \ + seqcount_init(&(x)->seqcount); \ + raw_spin_lock_init(&(x)->lock); \ + } while (0) + +#define DEFINE_RAW_SEQLOCK(x) \ + raw_seqlock_t x = __RAW_SEQLOCK_UNLOCKED(x) + #define __SEQLOCK_UNLOCKED(lockname) \ { \ .seqcount = SEQCNT_ZERO, \ @@ -210,6 +230,11 @@ typedef struct { /* * Read side functions for starting and finalizing a read side section. */ +static inline unsigned read_raw_seqbegin(const raw_seqlock_t *sl) +{ + return read_seqcount_begin(&sl->seqcount); +} + #ifndef CONFIG_PREEMPT_RT_FULL static inline unsigned read_seqbegin(const seqlock_t *sl) { @@ -238,6 +263,11 @@ repeat: } #endif +static inline unsigned read_raw_seqretry(const raw_seqlock_t *sl, unsigned start) +{ + return read_seqcount_retry(&sl->seqcount, start); +} + static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start) { return read_seqcount_retry(&sl->seqcount, start); @@ -248,6 +278,64 @@ static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start) * Acts like a normal spin_lock/unlock. * Don't need preempt_disable() because that is in the spin_lock already. */ +static inline void write_raw_seqlock(raw_seqlock_t *sl) +{ + raw_spin_lock(&sl->lock); + __write_seqcount_begin(&sl->seqcount); +} + +static inline void write_raw_sequnlock(raw_seqlock_t *sl) +{ + __write_seqcount_end(&sl->seqcount); + raw_spin_unlock(&sl->lock); +} + +static inline void write_raw_seqlock_bh(raw_seqlock_t *sl) +{ + raw_spin_lock_bh(&sl->lock); + __write_seqcount_begin(&sl->seqcount); +} + +static inline void write_raw_sequnlock_bh(raw_seqlock_t *sl) +{ + __write_seqcount_end(&sl->seqcount); + raw_spin_unlock_bh(&sl->lock); +} + +static inline void write_raw_seqlock_irq(raw_seqlock_t *sl) +{ + raw_spin_lock_irq(&sl->lock); + __write_seqcount_begin(&sl->seqcount); +} + +static inline void write_raw_sequnlock_irq(raw_seqlock_t *sl) +{ + __write_seqcount_end(&sl->seqcount); + raw_spin_unlock_irq(&sl->lock); +} + +static inline unsigned long __write_raw_seqlock_irqsave(raw_seqlock_t *sl) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&sl->lock, flags); + __write_seqcount_begin(&sl->seqcount); + return flags; +} + +#define write_raw_seqlock_irqsave(lock, flags) \ + do { flags = __write_raw_seqlock_irqsave(lock); } while (0) + +static inline void +write_raw_sequnlock_irqrestore(raw_seqlock_t *sl, unsigned long flags) +{ + __write_seqcount_end(&sl->seqcount); + raw_spin_unlock_irqrestore(&sl->lock, flags); +} + +/* + * non raw versions + */ static inline void write_seqlock(seqlock_t *sl) { spin_lock(&sl->lock); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
