mm, x86, ptrace, bts: defer branch trace stopping

When a ptraced task is unlinked, we need to stop branch tracing for
that task.

Since the unlink is called with interrupts disabled, and we need
interrupts enabled to stop branch tracing, we defer the work.

Collect all branch tracing related stuff in a branch tracing context.
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144550.712401000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/processor.h

@@ -458,10 +458,6 @@ struct thread_struct {
 /* Debug Store context; see include/asm-x86/ds.h; goes into MSR_IA32_DS_AREA */
 	struct ds_context	*ds_ctx;
 #endif /* CONFIG_X86_DS */
-#ifdef CONFIG_X86_PTRACE_BTS
-/* the signal to send on a bts buffer overflow */
-	unsigned int	bts_ovfl_signal;
-#endif /* CONFIG_X86_PTRACE_BTS */
 };
 
 static inline unsigned long native_get_debugreg(int regno)

include/linux/mm.h

@@ -13,6 +13,7 @@
 #include <linux/prio_tree.h>
 #include <linux/debug_locks.h>
 #include <linux/mm_types.h>
+#include <linux/sched.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -1321,6 +1322,6 @@ void vmemmap_populate_print_last(void);
 
 extern void *alloc_locked_buffer(size_t size);
 extern void free_locked_buffer(void *buffer, size_t size);
-extern void release_locked_buffer(void *buffer, size_t size);
+extern void refund_locked_buffer_memory(struct mm_struct *mm, size_t size);
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

include/linux/sched.h

@@ -96,8 +96,8 @@ struct exec_domain;
 struct futex_pi_state;
 struct robust_list_head;
 struct bio;
-struct bts_tracer;
 struct fs_struct;
+struct bts_context;
 
 /*
  * List of flags we want to share for kernel threads,
@@ -1210,12 +1210,7 @@ struct task_struct {
 	 * This is the tracer handle for the ptrace BTS extension.
 	 * This field actually belongs to the ptracer task.
 	 */
-	struct bts_tracer *bts;
-	/*
-	 * The buffer to hold the BTS data.
-	 */
-	void *bts_buffer;
-	size_t bts_size;
+	struct bts_context *bts;
 #endif /* CONFIG_X86_PTRACE_BTS */
 
 	/* PID/PID hash table linkage. */

mm/mlock.c

@@ -660,21 +660,20 @@ void *alloc_locked_buffer(size_t size)
 	return buffer;
 }
 
-void release_locked_buffer(void *buffer, size_t size)
+void refund_locked_buffer_memory(struct mm_struct *mm, size_t size)
 {
 	unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
 
-	down_write(&current->mm->mmap_sem);
+	down_write(&mm->mmap_sem);
 
-	current->mm->total_vm  -= pgsz;
-	current->mm->locked_vm -= pgsz;
+	mm->total_vm  -= pgsz;
+	mm->locked_vm -= pgsz;
 
-	up_write(&current->mm->mmap_sem);
+	up_write(&mm->mmap_sem);
 }
 
 void free_locked_buffer(void *buffer, size_t size)
 {
-	release_locked_buffer(buffer, size);
-
+	refund_locked_buffer_memory(current->mm, size);
 	kfree(buffer);
 }