From 91e6f1ce8657795cec83a81090c20cbaa8337c68 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Mon, 9 May 2016 18:10:00 -0400 Subject: [PATCH 1/3] ftracetest: Add instance created, delete, read and enable event test Add a new ftrace test that creates three threads. One that creates and removes an ftrace instance, one that reads the instance, and one that enables and disables events in the instance. This is a stress test for accessing and removing instances at the same time. Signed-off-by: Steven Rostedt --- .../ftrace/test.d/instances/instance-event.tc | 143 ++++++++++++++++++ 1 file changed, 143 insertions(+) create mode 100644 tools/testing/selftests/ftrace/test.d/instances/instance-event.tc diff --git a/tools/testing/selftests/ftrace/test.d/instances/instance-event.tc b/tools/testing/selftests/ftrace/test.d/instances/instance-event.tc new file mode 100644 index 000000000000..5f2abd03f16b --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/instances/instance-event.tc @@ -0,0 +1,143 @@ +#!/bin/sh +# description: Test creation and deletion of trace instances while setting an event + +if [ ! -d instances ] ; then + echo "no instance directory with this kernel" + exit_unsupported; +fi + +fail() { # mesg + rmdir foo 2>/dev/null + echo $1 + set -e + exit $FAIL +} + +cd instances + +# we don't want to fail on error +set +e + +mkdir x +rmdir x +result=$? + +if [ $result -ne 0 ]; then + echo "instance rmdir not supported" + exit_unsupported +fi + +instance_slam() { + while :; do + mkdir foo 2> /dev/null + rmdir foo 2> /dev/null + done +} + +instance_read() { + while :; do + cat foo/trace 1> /dev/null 2>&1 + done +} + +instance_set() { + while :; do + echo 1 > foo/events/sched/sched_switch + done 2> /dev/null +} + +instance_slam & +p1=$! +echo $p1 + +instance_set & +p2=$! +echo $p2 + +instance_read & +p3=$! +echo $p3 + +sleep 1 + +kill -1 $p3 +kill -1 $p2 +kill -1 $p1 + +echo "Wait for processes to finish" +wait $p1 $p2 $p3 +echo "all processes finished, wait for cleanup" +sleep 1 + +mkdir foo +ls foo > /dev/null +rmdir foo +if [ -d foo ]; then + fail "foo still exists" +fi +exit 0 + + + + +instance_slam() { + while :; do + mkdir x + mkdir y + mkdir z + rmdir x + rmdir y + rmdir z + done 2>/dev/null +} + +instance_slam & +x=`jobs -l` +p1=`echo $x | cut -d' ' -f2` +echo $p1 + +instance_slam & +x=`jobs -l | tail -1` +p2=`echo $x | cut -d' ' -f2` +echo $p2 + +instance_slam & +x=`jobs -l | tail -1` +p3=`echo $x | cut -d' ' -f2` +echo $p3 + +instance_slam & +x=`jobs -l | tail -1` +p4=`echo $x | cut -d' ' -f2` +echo $p4 + +instance_slam & +x=`jobs -l | tail -1` +p5=`echo $x | cut -d' ' -f2` +echo $p5 + +ls -lR >/dev/null +sleep 1 + +kill -1 $p1 +kill -1 $p2 +kill -1 $p3 +kill -1 $p4 +kill -1 $p5 + +echo "Wait for processes to finish" +wait $p1 $p2 $p3 $p4 $p5 +echo "all processes finished, wait for cleanup" + +mkdir x y z +ls x y z +rmdir x y z +for d in x y z; do + if [ -d $d ]; then + fail "instance $d still exists" + fi +done + +set -e + +exit 0 From 6112a300c9e41993cc0dc56ac393743d28381284 Mon Sep 17 00:00:00 2001 From: Soumya PN Date: Tue, 17 May 2016 21:31:14 +0530 Subject: [PATCH 2/3] ftrace: Don't disable irqs when taking the tasklist_lock read_lock In ftrace.c inside the function alloc_retstack_tasklist() (which will be invoked when function_graph tracing is on) the tasklist_lock is being held as reader while iterating through a list of threads. Here the lock is being held as reader with irqs disabled. The tasklist_lock is never write_locked in interrupt context so it is safe to not disable interrupts for the duration of read_lock in this block which, can be significant, given the block of code iterates through all threads. Hence changing the code to call read_lock() and read_unlock() instead of read_lock_irqsave() and read_unlock_irqrestore(). A similar change was made in commits: 8063e41d2ffc ("tracing: Change syscall_*regfunc() to check PF_KTHREAD and use for_each_process_thread()")' and 3472eaa1f12e ("sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock()")' Link: http://lkml.kernel.org/r/1463500874-77480-1-git-send-email-soumya.p.n@hpe.com Signed-off-by: Soumya PN Signed-off-by: Steven Rostedt --- kernel/trace/ftrace.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index b1870fbd2b67..a6804823a058 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5713,7 +5713,6 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) { int i; int ret = 0; - unsigned long flags; int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE; struct task_struct *g, *t; @@ -5729,7 +5728,7 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) } } - read_lock_irqsave(&tasklist_lock, flags); + read_lock(&tasklist_lock); do_each_thread(g, t) { if (start == end) { ret = -EAGAIN; @@ -5747,7 +5746,7 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) } while_each_thread(g, t); unlock: - read_unlock_irqrestore(&tasklist_lock, flags); + read_unlock(&tasklist_lock); free: for (i = start; i < end; i++) kfree(ret_stack_list[i]); From 8329e818f14926a6040df86b2668568bde342ebf Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Mon, 16 May 2016 23:00:35 -0400 Subject: [PATCH 3/3] ftrace/x86: Set ftrace_stub to weak to prevent gcc from using short jumps to it Matt Fleming reported seeing crashes when enabling and disabling function profiling which uses function graph tracer. Later Namhyung Kim hit a similar issue and he found that the issue was due to the jmp to ftrace_stub in ftrace_graph_call was only two bytes, and when it was changed to jump to the tracing code, it overwrote the ftrace_stub that was after it. Masami Hiramatsu bisected this down to a binutils change: 8dcea93252a9ea7dff57e85220a719e2a5e8ab41 is the first bad commit commit 8dcea93252a9ea7dff57e85220a719e2a5e8ab41 Author: H.J. Lu Date: Fri May 15 03:17:31 2015 -0700 Add -mshared option to x86 ELF assembler This patch adds -mshared option to x86 ELF assembler. By default, assembler will optimize out non-PLT relocations against defined non-weak global branch targets with default visibility. The -mshared option tells the assembler to generate code which may go into a shared library where all non-weak global branch targets with default visibility can be preempted. The resulting code is slightly bigger. This option only affects the handling of branch instructions. Declaring ftrace_stub as a weak call prevents gas from using two byte jumps to it, which would be converted to a jump to the function graph code. Link: http://lkml.kernel.org/r/20160516230035.1dbae571@gandalf.local.home Reported-by: Matt Fleming Reported-by: Namhyung Kim Tested-by: Matt Fleming Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt --- arch/x86/kernel/mcount_64.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S index ed48a9f465f8..61924222a9e1 100644 --- a/arch/x86/kernel/mcount_64.S +++ b/arch/x86/kernel/mcount_64.S @@ -182,7 +182,8 @@ GLOBAL(ftrace_graph_call) jmp ftrace_stub #endif -GLOBAL(ftrace_stub) +/* This is weak to keep gas from relaxing the jumps */ +WEAK(ftrace_stub) retq END(ftrace_caller)