diff options
Diffstat (limited to 'patches/trace-writeback--Block-cgroup-path-tracing-on-RT.patch')
| -rw-r--r-- | patches/trace-writeback--Block-cgroup-path-tracing-on-RT.patch | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/patches/trace-writeback--Block-cgroup-path-tracing-on-RT.patch b/patches/trace-writeback--Block-cgroup-path-tracing-on-RT.patch new file mode 100644 index 000000000000..d3c45f35b1dd --- /dev/null +++ b/patches/trace-writeback--Block-cgroup-path-tracing-on-RT.patch @@ -0,0 +1,55 @@ +Subject: trace/writeback: Block cgroup path tracing on RT +From: Thomas Gleixner <tglx@linutronix.de> +Date: Sun, 28 Feb 2016 15:14:43 +0100 + +Yang reported that with CGROUP_WRITEBACK enabled the tracer triggers the +following backtrace: + +BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:930 +in_atomic(): 1, irqs_disabled(): 0, pid: 625, name: kworker/u16:3 +INFO: lockdep is turned off. +Preemption disabled at:[<ffffffc000374a5c>] wb_writeback+0xec/0x830 + +CPU: 7 PID: 625 Comm: kworker/u16:3 Not tainted 4.4.1-rt5 #20 +Hardware name: Freescale Layerscape 2085a RDB Board (DT) +Workqueue: writeback wb_workfn (flush-7:0) +Call trace: +[<ffffffc00008d708>] dump_backtrace+0x0/0x200 +[<ffffffc00008d92c>] show_stack+0x24/0x30 +[<ffffffc0007b0f40>] dump_stack+0x88/0xa8 +[<ffffffc000127d74>] ___might_sleep+0x2ec/0x300 +[<ffffffc000d5d550>] rt_spin_lock+0x38/0xb8 +[<ffffffc0003e0548>] kernfs_path_len+0x30/0x90 +[<ffffffc00036b360>] trace_event_raw_event_writeback_work_class+0xe8/0x2e8 +[<ffffffc000374f90>] wb_writeback+0x620/0x830 +[<ffffffc000376224>] wb_workfn+0x61c/0x950 +[<ffffffc000110adc>] process_one_work+0x3ac/0xb30 +[<ffffffc0001112fc>] worker_thread+0x9c/0x7a8 +[<ffffffc00011a9e8>] kthread+0x190/0x1b0 +[<ffffffc000086ca0>] ret_from_fork+0x10/0x30 + +Yang proposed to provide an unlocked function for accessing the cgroup path, +but that'd involve synchronize_sched() in a syscall, which is not desired +either. There was some discussion about using the inode number or the cgroup +id, but so far we have no working solution. + +Disable the CGROUP_WRITEBACK path tracing for now when RT is enabled. + +Reported-by: Yang Shi <yang.shi@linaro.org> +Link: http://lkml.kernel.org/r/1456528481-15936-1-git-send-email-yang.shi@linaro.org +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +--- + include/trace/events/writeback.h | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +--- a/include/trace/events/writeback.h ++++ b/include/trace/events/writeback.h +@@ -132,7 +132,7 @@ DEFINE_EVENT(writeback_dirty_inode_templ + ); + + #ifdef CREATE_TRACE_POINTS +-#ifdef CONFIG_CGROUP_WRITEBACK ++#if defined(CONFIG_CGROUP_WRITEBACK) && !defined(CONFIG_PREEMPT_RT_FULL) + + static inline size_t __trace_wb_cgroup_size(struct bdi_writeback *wb) + { |