diff options
| -rw-r--r-- | kernel/trace/ring_buffer.c | 176 |
1 files changed, 9 insertions, 167 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 16b640d824f9..a4ada4f303c4 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -27,6 +27,7 @@ #include <linux/cpu.h> #include <linux/oom.h> +#include <asm/local64.h> #include <asm/local.h> /* @@ -463,27 +464,9 @@ enum { RB_CTX_MAX }; -#if BITS_PER_LONG == 32 -#define RB_TIME_32 -#endif - -/* To test on 64 bit machines */ -//#define RB_TIME_32 - -#ifdef RB_TIME_32 - -struct rb_time_struct { - local_t cnt; - local_t top; - local_t bottom; - local_t msb; -}; -#else -#include <asm/local64.h> struct rb_time_struct { local64_t time; }; -#endif typedef struct rb_time_struct rb_time_t; #define MAX_NEST 5 @@ -573,147 +556,14 @@ struct ring_buffer_iter { int missed_events; }; -#ifdef RB_TIME_32 - -/* - * On 32 bit machines, local64_t is very expensive. As the ring - * buffer doesn't need all the features of a true 64 bit atomic, - * on 32 bit, it uses these functions (64 still uses local64_t). - * - * For the ring buffer, 64 bit required operations for the time is - * the following: - * - * - Reads may fail if it interrupted a modification of the time stamp. - * It will succeed if it did not interrupt another write even if - * the read itself is interrupted by a write. - * It returns whether it was successful or not. - * - * - Writes always succeed and will overwrite other writes and writes - * that were done by events interrupting the current write. - * - * - A write followed by a read of the same time stamp will always succeed, - * but may not contain the same value. - * - * - A cmpxchg will fail if it interrupted another write or cmpxchg. - * Other than that, it acts like a normal cmpxchg. - * - * The 60 bit time stamp is broken up by 30 bits in a top and bottom half - * (bottom being the least significant 30 bits of the 60 bit time stamp). - * - * The two most significant bits of each half holds a 2 bit counter (0-3). - * Each update will increment this counter by one. - * When reading the top and bottom, if the two counter bits match then the - * top and bottom together make a valid 60 bit number. - */ -#define RB_TIME_SHIFT 30 -#define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1) -#define RB_TIME_MSB_SHIFT 60 - -static inline int rb_time_cnt(unsigned long val) -{ - return (val >> RB_TIME_SHIFT) & 3; -} - -static inline u64 rb_time_val(unsigned long top, unsigned long bottom) -{ - u64 val; - - val = top & RB_TIME_VAL_MASK; - val <<= RB_TIME_SHIFT; - val |= bottom & RB_TIME_VAL_MASK; - - return val; -} - -static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt) -{ - unsigned long top, bottom, msb; - unsigned long c; - - /* - * If the read is interrupted by a write, then the cnt will - * be different. Loop until both top and bottom have been read - * without interruption. - */ - do { - c = local_read(&t->cnt); - top = local_read(&t->top); - bottom = local_read(&t->bottom); - msb = local_read(&t->msb); - } while (c != local_read(&t->cnt)); - - *cnt = rb_time_cnt(top); - - /* If top, msb or bottom counts don't match, this interrupted a write */ - if (*cnt != rb_time_cnt(msb) || *cnt != rb_time_cnt(bottom)) - return false; - - /* The shift to msb will lose its cnt bits */ - *ret = rb_time_val(top, bottom) | ((u64)msb << RB_TIME_MSB_SHIFT); - return true; -} - -static bool rb_time_read(rb_time_t *t, u64 *ret) -{ - unsigned long cnt; - - return __rb_time_read(t, ret, &cnt); -} - -static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt) -{ - return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT); -} - -static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom, - unsigned long *msb) -{ - *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK); - *bottom = (unsigned long)(val & RB_TIME_VAL_MASK); - *msb = (unsigned long)(val >> RB_TIME_MSB_SHIFT); -} - -static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt) -{ - val = rb_time_val_cnt(val, cnt); - local_set(t, val); -} - -static void rb_time_set(rb_time_t *t, u64 val) -{ - unsigned long cnt, top, bottom, msb; - - rb_time_split(val, &top, &bottom, &msb); - - /* Writes always succeed with a valid number even if it gets interrupted. */ - do { - cnt = local_inc_return(&t->cnt); - rb_time_val_set(&t->top, top, cnt); - rb_time_val_set(&t->bottom, bottom, cnt); - rb_time_val_set(&t->msb, val >> RB_TIME_MSB_SHIFT, cnt); - } while (cnt != local_read(&t->cnt)); -} - -static inline bool -rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set) -{ - return local_try_cmpxchg(l, &expect, set); -} - -#else /* 64 bits */ - -/* local64_t always succeeds */ - -static inline bool rb_time_read(rb_time_t *t, u64 *ret) +static inline void rb_time_read(rb_time_t *t, u64 *ret) { *ret = local64_read(&t->time); - return true; } static void rb_time_set(rb_time_t *t, u64 val) { local64_set(&t->time, val); } -#endif /* * Enable this to make sure that the event passed to @@ -820,10 +670,7 @@ u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer, WARN_ONCE(1, "nest (%d) greater than max", nest); fail: - /* Can only fail on 32 bit */ - if (!rb_time_read(&cpu_buffer->write_stamp, &ts)) - /* Screw it, just read the current time */ - ts = rb_time_stamp(cpu_buffer->buffer); + rb_time_read(&cpu_buffer->write_stamp, &ts); return ts; } @@ -2820,7 +2667,7 @@ rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer, (unsigned long long)info->ts, (unsigned long long)info->before, (unsigned long long)info->after, - (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0), + (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}), sched_clock_stable() ? "" : "If you just came from a suspend/resume,\n" "please switch to the trace global clock:\n" @@ -3497,16 +3344,14 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event; struct buffer_page *tail_page; unsigned long tail, write, w; - bool a_ok; - bool b_ok; /* Don't let the compiler play games with cpu_buffer->tail_page */ tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK; barrier(); - b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before); - a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); + rb_time_read(&cpu_buffer->before_stamp, &info->before); + rb_time_read(&cpu_buffer->write_stamp, &info->after); barrier(); info->ts = rb_time_stamp(cpu_buffer->buffer); @@ -3521,7 +3366,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, if (!w) { /* Use the sub-buffer timestamp */ info->delta = 0; - } else if (unlikely(!a_ok || !b_ok || info->before != info->after)) { + } else if (unlikely(info->before != info->after)) { info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND; info->length += RB_LEN_TIME_EXTEND; } else { @@ -3570,8 +3415,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, /* SLOW PATH - Interrupted between A and C */ /* Save the old before_stamp */ - a_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before); - RB_WARN_ON(cpu_buffer, !a_ok); + rb_time_read(&cpu_buffer->before_stamp, &info->before); /* * Read a new timestamp and update the before_stamp to make @@ -3583,9 +3427,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, rb_time_set(&cpu_buffer->before_stamp, ts); barrier(); - /*E*/ a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); - /* Was interrupted before here, write_stamp must be valid */ - RB_WARN_ON(cpu_buffer, !a_ok); + /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after); barrier(); /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) && info->after == info->before && info->after < ts) { |