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authorFrederic Weisbecker <fweisbec@gmail.com>2009-12-09 09:25:48 +0100
committerIngo Molnar <mingo@elte.hu>2009-12-09 09:48:20 +0100
commit44234adcdce38f83c56e05f808ce656175b4beeb (patch)
treecaff2ca7bbf4bf7c0b12652caf739bcc6db5f4d3 /include
parentc937fe20cb6d9e24c6ad5f9f0c64d64c78411057 (diff)
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hw-breakpoints: Modify breakpoints without unregistering them
Currently, when ptrace needs to modify a breakpoint, like disabling it, changing its address, type or len, it calls modify_user_hw_breakpoint(). This latter will perform the heavy and racy task of unregistering the old breakpoint and registering a new one. This is racy as someone else might steal the reserved breakpoint slot under us, which is undesired as the breakpoint is only supposed to be modified, sometimes in the middle of a debugging workflow. We don't want our slot to be stolen in the middle. So instead of unregistering/registering the breakpoint, just disable it while we modify its breakpoint fields and re-enable it after if necessary. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Prasad <prasad@linux.vnet.ibm.com> LKML-Reference: <1260347148-5519-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/linux/hw_breakpoint.h4
-rw-r--r--include/linux/perf_event.h5
2 files changed, 6 insertions, 3 deletions
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index 42da1ce19ec..69f07a9f127 100644
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -55,7 +55,7 @@ register_user_hw_breakpoint(struct perf_event_attr *attr,
struct task_struct *tsk);
/* FIXME: only change from the attr, and don't unregister */
-extern struct perf_event *
+extern int
modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr);
/*
@@ -91,7 +91,7 @@ static inline struct perf_event *
register_user_hw_breakpoint(struct perf_event_attr *attr,
perf_overflow_handler_t triggered,
struct task_struct *tsk) { return NULL; }
-static inline struct perf_event *
+static inline int
modify_user_hw_breakpoint(struct perf_event *bp,
struct perf_event_attr *attr) { return NULL; }
static inline struct perf_event *
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index bf3329413e1..64a53f74c9a 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -872,6 +872,8 @@ extern void perf_output_copy(struct perf_output_handle *handle,
const void *buf, unsigned int len);
extern int perf_swevent_get_recursion_context(void);
extern void perf_swevent_put_recursion_context(int rctx);
+extern void perf_event_enable(struct perf_event *event);
+extern void perf_event_disable(struct perf_event *event);
#else
static inline void
perf_event_task_sched_in(struct task_struct *task, int cpu) { }
@@ -902,7 +904,8 @@ static inline void perf_event_fork(struct task_struct *tsk) { }
static inline void perf_event_init(void) { }
static inline int perf_swevent_get_recursion_context(void) { return -1; }
static inline void perf_swevent_put_recursion_context(int rctx) { }
-
+static inline void perf_event_enable(struct perf_event *event) { }
+static inline void perf_event_disable(struct perf_event *event) { }
#endif
#define perf_output_put(handle, x) \