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Subject[PATCH 23/40] kgdb: Add the ability to schedule a breakpoint via a tasklet
Date
Some kgdb I/O modules require the ability to create a breakpoint
tasklet, such as kgdboc and external modules such as kgdboe. The
breakpoint tasklet is used as an asynchronous entry point into the
debugger which will have a different function scope than the current
execution path where it might not be safe to have an inline
breakpoint. This is true of some of the kgdb I/O drivers which share
code with kgdb and rest of the kernel users.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
---
include/linux/kgdb.h | 1 +
kernel/debug/debug_core.c | 26 ++++++++++++++++++++++++++
2 files changed, 27 insertions(+), 0 deletions(-)
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index e4e9206..076f3c6 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -270,6 +270,7 @@ extern int kgdb_mem2hex(char *mem, char *buf, int count);
extern int kgdb_hex2mem(char *buf, char *mem, int count);

extern int kgdb_isremovedbreak(unsigned long addr);
+extern void kgdb_schedule_breakpoint(void);

extern int
kgdb_handle_exception(int ex_vector, int signo, int err_code,
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 5ceaa0f..e02c552 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -112,6 +112,7 @@ atomic_t kgdb_active = ATOMIC_INIT(-1);
*/
static atomic_t passive_cpu_wait[NR_CPUS];
static atomic_t cpu_in_kgdb[NR_CPUS];
+static atomic_t kgdb_break_tasklet_var;
atomic_t kgdb_setting_breakpoint;

struct task_struct *kgdb_usethread;
@@ -776,6 +777,31 @@ static void kgdb_unregister_callbacks(void)
}
}

+/*
+ * There are times a tasklet needs to be used vs a compiled in
+ * break point so as to cause an exception outside a kgdb I/O module,
+ * such as is the case with kgdboe, where calling a breakpoint in the
+ * I/O driver itself would be fatal.
+ */
+static void kgdb_tasklet_bpt(unsigned long ing)
+{
+ kgdb_breakpoint();
+ atomic_set(&kgdb_break_tasklet_var, 0);
+}
+
+static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
+
+void kgdb_schedule_breakpoint(void)
+{
+ if (atomic_read(&kgdb_break_tasklet_var) ||
+ atomic_read(&kgdb_active) != -1 ||
+ atomic_read(&kgdb_setting_breakpoint))
+ return;
+ atomic_inc(&kgdb_break_tasklet_var);
+ tasklet_schedule(&kgdb_tasklet_breakpoint);
+}
+EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
+
static void kgdb_initial_breakpoint(void)
{
kgdb_break_asap = 0;
--
1.6.3.1.9.g95405b


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