[PATCH v2 5/5] tracing/user_events: Add persist flag documentation
From: Beau Belgrave <hidden>
Date: 2023-06-05 23:39:22
Also in:
lkml
Subsystem:
documentation, the rest, tracing · Maintainers:
Jonathan Corbet, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
There is now a flag for user_events to use when registering events to have events continue to exist upon the last reference put. Add the new flag, USER_EVENT_REG_PERSIST, to user_events documentation files to let people know when to use it. Signed-off-by: Beau Belgrave <redacted> --- Documentation/trace/user_events.rst | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst
index f79987e16cf4..6736e5a32293 100644
--- a/Documentation/trace/user_events.rst
+++ b/Documentation/trace/user_events.rst@@ -39,6 +39,14 @@ DIAG_IOCSREG. This command takes a packed struct user_reg as an argument:: + enum user_reg_flag { + /* Event will not delete upon last reference closing */ + USER_EVENT_REG_PERSIST = 1U << 0, + + /* This value or above is currently non-ABI */ + USER_EVENT_REG_MAX = 1U << 1, + }; + struct user_reg { /* Input: Size of the user_reg structure being used */ __u32 size;
@@ -49,7 +57,7 @@ This command takes a packed struct user_reg as an argument:: /* Input: Enable size in bytes at address */ __u8 enable_size; - /* Input: Flags for future use, set to 0 */ + /* Input: Flags can be any of the above user_reg_flag values */ __u16 flags; /* Input: Address to update when enabled */
@@ -73,10 +81,13 @@ The struct user_reg requires all the above inputs to be set appropriately. This must be 4 (32-bit) or 8 (64-bit). 64-bit values are only allowed to be used on 64-bit kernels, however, 32-bit can be used on all kernels. -+ flags: The flags to use, if any. For the initial version this must be 0. - Callers should first attempt to use flags and retry without flags to ensure - support for lower versions of the kernel. If a flag is not supported -EINVAL - is returned. ++ flags: The flags to use, if any. Callers should first attempt to use flags + and retry without flags to ensure support for lower versions of the kernel. + If a flag is not supported -EINVAL is returned. + + **USER_EVENT_REG_PERSIST** + When the last reference is closed for the event, the event will continue + to exist until a delete IOCTL is issued by a user. + enable_addr: The address of the value to use to reflect event status. This must be naturally aligned and write accessible within the user program.
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2.25.1