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Diffstat (limited to 'Documentation/trace/ftrace-uses.rst')
| -rw-r--r-- | Documentation/trace/ftrace-uses.rst | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/trace/ftrace-uses.rst b/Documentation/trace/ftrace-uses.rst index 1fbc69894eed..2a05e770618a 100644 --- a/Documentation/trace/ftrace-uses.rst +++ b/Documentation/trace/ftrace-uses.rst @@ -146,7 +146,7 @@ FTRACE_OPS_FL_RECURSION_SAFE itself or any nested functions that those functions call. If this flag is set, it is possible that the callback will also - be called with preemption enabled (when CONFIG_PREEMPT is set), + be called with preemption enabled (when CONFIG_PREEMPTION is set), but this is not guaranteed. FTRACE_OPS_FL_IPMODIFY @@ -170,6 +170,14 @@ FTRACE_OPS_FL_RCU a callback may be executed and RCU synchronization will not protect it. +FTRACE_OPS_FL_PERMANENT + If this is set on any ftrace ops, then the tracing cannot disabled by + writing 0 to the proc sysctl ftrace_enabled. Equally, a callback with + the flag set cannot be registered if ftrace_enabled is 0. + + Livepatch uses it not to lose the function redirection, so the system + stays protected. + Filtering which functions to trace ================================== |