From 8e9509c827a28e2f365c203c04224f9e9dd1b63a Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Thu, 17 Jul 2008 13:26:50 +0200 Subject: [PATCH 1/4] ftrace: fix merge buglet -tip testing found a bootup hang here: initcall anon_inode_init+0x0/0x130 returned 0 after 0 msecs calling acpi_event_init+0x0/0x57 the bootup should have continued with: initcall acpi_event_init+0x0/0x57 returned 0 after 45 msecs but it hung hard there instead. bisection led to this commit: | commit 5806b81ac1c0c52665b91723fd4146a4f86e386b | Merge: d14c8a6... 6712e29... | Author: Ingo Molnar <mingo@elte.hu> | Date: Mon Jul 14 16:11:52 2008 +0200 | Merge branch 'auto-ftrace-next' into tracing/for-linus turns out that i made this mistake in the merge: ifdef CONFIG_FTRACE # Do not profile debug utilities CFLAGS_REMOVE_tsc_64.o = -pg CFLAGS_REMOVE_tsc_32.o = -pg those two files got unified meanwhile - so the dont-profile annotation got lost. The proper rule is: CFLAGS_REMOVE_tsc.o = -pg i guess this could have been caught sooner if the CFLAGS_REMOVE* kbuild rule aborted the build if it met a target that does not exist anymore? Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/kernel/Makefile | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 5112c84f5421..da140611bb57 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -8,8 +8,7 @@ CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE) ifdef CONFIG_FTRACE # Do not profile debug utilities -CFLAGS_REMOVE_tsc_64.o = -pg -CFLAGS_REMOVE_tsc_32.o = -pg +CFLAGS_REMOVE_tsc.o = -pg CFLAGS_REMOVE_rtc.o = -pg endif From 9fa111372a54f695f65e0de2f2a2108fe6cf3584 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Thu, 17 Jul 2008 17:38:17 +0200 Subject: [PATCH 2/4] ftrace: fix lockup with MAXSMP MAXSMP brings in lots of use of various bitops in smp_processor_id() and friends - causing ftrace to lock up during bootup: calling anon_inode_init+0x0/0x130 initcall anon_inode_init+0x0/0x130 returned 0 after 0 msecs calling acpi_event_init+0x0/0x57 [ hard hang ] So exclude the bitops facilities from tracing. Signed-off-by: Ingo Molnar <mingo@elte.hu> --- lib/Makefile | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/Makefile b/lib/Makefile index 2c62a9c06fbe..d90d31102e05 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -15,6 +15,9 @@ CFLAGS_REMOVE_string.o = -pg CFLAGS_REMOVE_spinlock_debug.o = -pg CFLAGS_REMOVE_list_debug.o = -pg CFLAGS_REMOVE_debugobjects.o = -pg +CFLAGS_REMOVE_find_next_bit.o = -pg +CFLAGS_REMOVE_cpumask.o = -pg +CFLAGS_REMOVE_bitmap.o = -pg endif lib-$(CONFIG_MMU) += ioremap.o From c349e0a01c3e0f70913db6a5bb61ab204e0602de Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Tue, 15 Apr 2008 22:39:31 +0200 Subject: [PATCH 3/4] ftrace: do not trace scheduler functions do not trace scheduler functions - it's still a bit fragile and can lock up with: http://redhat.com/~mingo/misc/config-Thu_Jul_17_13_34_52_CEST_2008 Signed-off-by: Ingo Molnar <mingo@elte.hu> --- kernel/Makefile | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/Makefile b/kernel/Makefile index 0a7ed838984b..985ddb7da4d0 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -11,8 +11,6 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \ hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \ notifier.o ksysfs.o pm_qos_params.o sched_clock.o -CFLAGS_REMOVE_sched.o = -mno-spe - ifdef CONFIG_FTRACE # Do not trace debug files and internal ftrace files CFLAGS_REMOVE_lockdep.o = -pg @@ -21,6 +19,7 @@ CFLAGS_REMOVE_mutex-debug.o = -pg CFLAGS_REMOVE_rtmutex-debug.o = -pg CFLAGS_REMOVE_cgroup-debug.o = -pg CFLAGS_REMOVE_sched_clock.o = -pg +CFLAGS_REMOVE_sched.o = -mno-spe -pg endif obj-$(CONFIG_SYSCTL_SYSCALL_CHECK) += sysctl_check.o From 2464a609ded094204a3aed24823745ec58e3c879 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Thu, 17 Jul 2008 17:40:48 +0200 Subject: [PATCH 4/4] ftrace: do not trace library functions make function tracing more robust: do not trace library functions. We've already got a sizable list of exceptions: ifdef CONFIG_FTRACE # Do not profile string.o, since it may be used in early boot or vdso CFLAGS_REMOVE_string.o = -pg # Also do not profile any debug utilities CFLAGS_REMOVE_spinlock_debug.o = -pg CFLAGS_REMOVE_list_debug.o = -pg CFLAGS_REMOVE_debugobjects.o = -pg CFLAGS_REMOVE_find_next_bit.o = -pg CFLAGS_REMOVE_cpumask.o = -pg CFLAGS_REMOVE_bitmap.o = -pg endif ... and the pattern has been that random library functionality showed up in ftrace's critical path (outside of its recursion check), causing hard to debug lockups. So be a bit defensive about it and exclude all lib/*.o functions by default. It's not that they are overly interesting for tracing purposes anyway. Specific ones can still be traced, in an opt-in manner. Signed-off-by: Ingo Molnar <mingo@elte.hu> --- lib/Makefile | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/lib/Makefile b/lib/Makefile index d90d31102e05..818c4d455518 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -2,24 +2,17 @@ # Makefile for some libs needed in the kernel. # +ifdef CONFIG_FTRACE +ORIG_CFLAGS := $(KBUILD_CFLAGS) +KBUILD_CFLAGS = $(subst -pg,,$(ORIG_CFLAGS)) +endif + lib-y := ctype.o string.o vsprintf.o cmdline.o \ rbtree.o radix-tree.o dump_stack.o \ idr.o int_sqrt.o extable.o prio_tree.o \ sha1.o irq_regs.o reciprocal_div.o argv_split.o \ proportions.o prio_heap.o ratelimit.o -ifdef CONFIG_FTRACE -# Do not profile string.o, since it may be used in early boot or vdso -CFLAGS_REMOVE_string.o = -pg -# Also do not profile any debug utilities -CFLAGS_REMOVE_spinlock_debug.o = -pg -CFLAGS_REMOVE_list_debug.o = -pg -CFLAGS_REMOVE_debugobjects.o = -pg -CFLAGS_REMOVE_find_next_bit.o = -pg -CFLAGS_REMOVE_cpumask.o = -pg -CFLAGS_REMOVE_bitmap.o = -pg -endif - lib-$(CONFIG_MMU) += ioremap.o lib-$(CONFIG_SMP) += cpumask.o