rb_reserve_next

Name:rb_reserve_next_event

Proto:static __always_inline struct ring_buffer_event *rb_reserve_next_event(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer, unsigned long length)

Type:struct ring_buffer_event

Parameter:

Type	Parameter	Name
struct ring_buffer *	buffer
struct ring_buffer_per_cpu *	cpu_buffer
unsigned long	length

2877

nr_loops = 0

2880

rb_start_commit(cpu_buffer)

2897

length = rb_calculate_event_length(length)

2898

again :

2899

add_timestamp = 0

2900

delta = 0

2911

If uffer may be either ring_buffer or ring_buffer_per_cpu (cpu_buffer, ++nr_loops > 1000) Then Go to out_fail

2914

ts = rb_time_stamp(buffer)

2915

diff = ts - write_stamp

2918

The "volatile" is due to gcc bugs ()

2920

If ring_buffer_time_stamp_abs(buffer) Then

2921

delta = ts

2922

rb_handle_timestamp(cpu_buffer, & info)

2923

Else If Value is more likely to compile time(ts >= write_stamp) Then

2925

delta = diff

2926

If Value for the false possibility is greater at compile time(We need to fit the time_stamp delta into 27 bits.) Then rb_handle_timestamp(cpu_buffer, & info)

2930

event = __rb_reserve_next(cpu_buffer, & info)

2932

If Value for the false possibility is greater at compile time(PTR_ERR(event) == - EAGAIN) Then

2933

If add_timestamp Then length -= RB_LEN_TIME_EXTEND

2935

Go to again

2938

If Not event Then Go to out_fail

2941

Return event

2943

out_fail :

2944

rb_end_commit(cpu_buffer)

2945

Return NULL

**Caller**
Name	Describe
ring_buffer_lock_reserve	g_buffer_lock_reserve - reserve a part of the buffer@buffer: the ring buffer to reserve from@length: the length of the data to reserve (excluding event header)* Returns a reserved event on the ring buffer to copy directly to
ring_buffer_write	g_buffer_write - write data to the buffer without reserving*@buffer: The ring buffer to write to

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