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authorJeff Dike <jdike@addtoit.com>2008-02-04 22:30:36 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 09:44:25 -0800
commitc11274655558e72d8d4a598c0077874c094d97d5 (patch)
treec7d13b5aeb4994a1c03ec6a5edd723ba06fd94da /arch/um
parentc9a3072d13e4b8a6549ecc1db6390a55c7ee2ddf (diff)
uml: implement get_wchan
Implement get_wchan - the algorithm is similar to x86. It starts with the stack pointer of the process in question and looks above that for addresses that are kernel text. The second one which isn't in the scheduler is the one that's returned. The first one is ignored because that will be UML's own context switching routine. Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/um')
-rw-r--r--arch/um/kernel/process.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 0eae00b3e58..c7ea7f2a894 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -459,3 +459,38 @@ unsigned long arch_align_stack(unsigned long sp)
return sp & ~0xf;
}
#endif
+
+unsigned long get_wchan(struct task_struct *p)
+{
+ unsigned long stack_page, sp, ip;
+ bool seen_sched = 0;
+
+ if ((p == NULL) || (p == current) || (p->state == TASK_RUNNING))
+ return 0;
+
+ stack_page = (unsigned long) task_stack_page(p);
+ /* Bail if the process has no kernel stack for some reason */
+ if (stack_page == 0)
+ return 0;
+
+ sp = p->thread.switch_buf->JB_SP;
+ /*
+ * Bail if the stack pointer is below the bottom of the kernel
+ * stack for some reason
+ */
+ if (sp < stack_page)
+ return 0;
+
+ while (sp < stack_page + THREAD_SIZE) {
+ ip = *((unsigned long *) sp);
+ if (in_sched_functions(ip))
+ /* Ignore everything until we're above the scheduler */
+ seen_sched = 1;
+ else if (kernel_text_address(ip) && seen_sched)
+ return ip;
+
+ sp += sizeof(unsigned long);
+ }
+
+ return 0;
+}