From: Mathieu Desnoyers Date: Thu, 11 May 2017 20:50:50 +0000 (-0400) Subject: Fix: add "flush empty" ioctl for stream intersection X-Git-Tag: v2.8.6~11 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=eac992672a4466ab1404739b81d4dd49939a3cbd;p=lttng-modules.git Fix: add "flush empty" ioctl for stream intersection Changing the behavior of the "snapshot" lttng command to implicitly do a buffer "flush" (even when current packet is empty) had unwanted side-effects: for instance, the snapshot ABI is used by the live timer to grab the buffer positions, and we don't want to generate useless empty packets in that scenario. Therefore, add the "flush empty" behavior as a new ioctl to the ring buffer. This allows lttng-tools to perform buffer flush (even for empty packets) when it needs to. Given that this new ioctl is added within stable branches as well, lttng-tools always need to handle "-ENOSYS" gracefully. Signed-off-by: Mathieu Desnoyers --- diff --git a/lib/ringbuffer/frontend_internal.h b/lib/ringbuffer/frontend_internal.h index b13edd10..4b367aea 100644 --- a/lib/ringbuffer/frontend_internal.h +++ b/lib/ringbuffer/frontend_internal.h @@ -158,6 +158,8 @@ void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf, extern void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf); +extern +void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf); /* Buffer write helpers */ diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c index 922940d1..97c963c8 100644 --- a/lib/ringbuffer/ring_buffer_frontend.c +++ b/lib/ringbuffer/ring_buffer_frontend.c @@ -1784,12 +1784,20 @@ static void _lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf, put_online_cpus(); } +/* Switch sub-buffer if current sub-buffer is non-empty. */ void lib_ring_buffer_switch_remote(struct lib_ring_buffer *buf) { _lib_ring_buffer_switch_remote(buf, SWITCH_ACTIVE); } EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_remote); +/* Switch sub-buffer even if current sub-buffer is empty. */ +void lib_ring_buffer_switch_remote_empty(struct lib_ring_buffer *buf) +{ + _lib_ring_buffer_switch_remote(buf, SWITCH_FLUSH); +} +EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_remote_empty); + /* * Returns : * 0 if ok diff --git a/lib/ringbuffer/ring_buffer_vfs.c b/lib/ringbuffer/ring_buffer_vfs.c index f1a8bab7..4b1aa38e 100644 --- a/lib/ringbuffer/ring_buffer_vfs.c +++ b/lib/ringbuffer/ring_buffer_vfs.c @@ -270,6 +270,9 @@ long lib_ring_buffer_ioctl(struct file *filp, unsigned int cmd, case RING_BUFFER_FLUSH: lib_ring_buffer_switch_remote(buf); return 0; + case RING_BUFFER_FLUSH_EMPTY: + lib_ring_buffer_switch_remote_empty(buf); + return 0; default: return -ENOIOCTLCMD; } @@ -415,6 +418,9 @@ long lib_ring_buffer_compat_ioctl(struct file *filp, unsigned int cmd, case RING_BUFFER_COMPAT_FLUSH: lib_ring_buffer_switch_remote(buf); return 0; + case RING_BUFFER_COMPAT_FLUSH_EMPTY: + lib_ring_buffer_switch_remote_empty(buf); + return 0; default: return -ENOIOCTLCMD; } diff --git a/lib/ringbuffer/vfs.h b/lib/ringbuffer/vfs.h index 5444a4b2..2387afc2 100644 --- a/lib/ringbuffer/vfs.h +++ b/lib/ringbuffer/vfs.h @@ -111,10 +111,13 @@ ssize_t vfs_lib_ring_buffer_splice_read(struct file *in, loff_t *ppos, #define RING_BUFFER_GET_MMAP_LEN _IOR(0xF6, 0x0A, unsigned long) /* returns the offset of the subbuffer belonging to the mmap reader. */ #define RING_BUFFER_GET_MMAP_READ_OFFSET _IOR(0xF6, 0x0B, unsigned long) -/* flush the current sub-buffer */ +/* Flush the current sub-buffer, if non-empty. */ #define RING_BUFFER_FLUSH _IO(0xF6, 0x0C) /* Get the current version of the metadata cache (after a get_next). */ #define RING_BUFFER_GET_METADATA_VERSION _IOR(0xF6, 0x0D, uint64_t) +/* Reserved: (0xF6, 0x0E). */ +/* Flush the current sub-buffer, even if empty. */ +#define RING_BUFFER_FLUSH_EMPTY _IO(0xF6, 0x0F) #ifdef CONFIG_COMPAT /* Get a snapshot of the current ring buffer producer and consumer positions */ @@ -145,10 +148,13 @@ ssize_t vfs_lib_ring_buffer_splice_read(struct file *in, loff_t *ppos, #define RING_BUFFER_COMPAT_GET_MMAP_LEN _IOR(0xF6, 0x0A, compat_ulong_t) /* returns the offset of the subbuffer belonging to the mmap reader. */ #define RING_BUFFER_COMPAT_GET_MMAP_READ_OFFSET _IOR(0xF6, 0x0B, compat_ulong_t) -/* flush the current sub-buffer */ +/* Flush the current sub-buffer, if non-empty. */ #define RING_BUFFER_COMPAT_FLUSH RING_BUFFER_FLUSH /* Get the current version of the metadata cache (after a get_next). */ #define RING_BUFFER_COMPAT_GET_METADATA_VERSION RING_BUFFER_GET_METADATA_VERSION +/* Flush the current sub-buffer, even if empty. */ +#define RING_BUFFER_COMPAT_FLUSH_EMPTY \ + RING_BUFFER_FLUSH_EMPTY #endif /* CONFIG_COMPAT */ #endif /* _LIB_RING_BUFFER_VFS_H */ diff --git a/lttng-abi.c b/lttng-abi.c index fc72e29b..6a255ae5 100644 --- a/lttng-abi.c +++ b/lttng-abi.c @@ -681,6 +681,7 @@ long lttng_metadata_ring_buffer_ioctl(struct file *filp, */ return -ENOSYS; } + case RING_BUFFER_FLUSH_EMPTY: /* Fall-through. */ case RING_BUFFER_FLUSH: { struct lttng_metadata_stream *stream = filp->private_data; @@ -757,6 +758,7 @@ long lttng_metadata_ring_buffer_compat_ioctl(struct file *filp, */ return -ENOSYS; } + case RING_BUFFER_FLUSH_EMPTY: /* Fall-through. */ case RING_BUFFER_FLUSH: { struct lttng_metadata_stream *stream = filp->private_data;