Revision f17a5194859a82afe4164e938b92035b86c55794 authored by Steven Rostedt (Red Hat) on 31 May 2013, 01:10:37 UTC, committed by Steven Rostedt on 06 June 2013, 16:35:30 UTC
The irqsoff tracer records the max time that interrupts are disabled. There are hooks in the assembly code that calls back into the tracer when interrupts are disabled or enabled. When they are enabled, the tracer checks if the amount of time they were disabled is larger than the previous recorded max interrupts off time. If it is, it creates a snapshot of the currently running trace to store where the last largest interrupts off time was held and how it happened. During testing, this RCU lockdep dump appeared: [ 1257.829021] =============================== [ 1257.829021] [ INFO: suspicious RCU usage. ] [ 1257.829021] 3.10.0-rc1-test+ #171 Tainted: G W [ 1257.829021] ------------------------------- [ 1257.829021] /home/rostedt/work/git/linux-trace.git/include/linux/rcupdate.h:780 rcu_read_lock() used illegally while idle! [ 1257.829021] [ 1257.829021] other info that might help us debug this: [ 1257.829021] [ 1257.829021] [ 1257.829021] RCU used illegally from idle CPU! [ 1257.829021] rcu_scheduler_active = 1, debug_locks = 0 [ 1257.829021] RCU used illegally from extended quiescent state! [ 1257.829021] 2 locks held by trace-cmd/4831: [ 1257.829021] #0: (max_trace_lock){......}, at: [<ffffffff810e2b77>] stop_critical_timing+0x1a3/0x209 [ 1257.829021] #1: (rcu_read_lock){.+.+..}, at: [<ffffffff810dae5a>] __update_max_tr+0x88/0x1ee [ 1257.829021] [ 1257.829021] stack backtrace: [ 1257.829021] CPU: 3 PID: 4831 Comm: trace-cmd Tainted: G W 3.10.0-rc1-test+ #171 [ 1257.829021] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007 [ 1257.829021] 0000000000000001 ffff880065f49da8 ffffffff8153dd2b ffff880065f49dd8 [ 1257.829021] ffffffff81092a00 ffff88006bd78680 ffff88007add7500 0000000000000003 [ 1257.829021] ffff88006bd78680 ffff880065f49e18 ffffffff810daebf ffffffff810dae5a [ 1257.829021] Call Trace: [ 1257.829021] [<ffffffff8153dd2b>] dump_stack+0x19/0x1b [ 1257.829021] [<ffffffff81092a00>] lockdep_rcu_suspicious+0x109/0x112 [ 1257.829021] [<ffffffff810daebf>] __update_max_tr+0xed/0x1ee [ 1257.829021] [<ffffffff810dae5a>] ? __update_max_tr+0x88/0x1ee [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810dbf85>] update_max_tr_single+0x11d/0x12d [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810e2b15>] stop_critical_timing+0x141/0x209 [ 1257.829021] [<ffffffff8109569a>] ? trace_hardirqs_on+0xd/0xf [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810e3057>] time_hardirqs_on+0x2a/0x2f [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff8109550c>] trace_hardirqs_on_caller+0x16/0x197 [ 1257.829021] [<ffffffff8109569a>] trace_hardirqs_on+0xd/0xf [ 1257.829021] [<ffffffff811002b9>] user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810029b4>] do_notify_resume+0x92/0x97 [ 1257.829021] [<ffffffff8154bdca>] int_signal+0x12/0x17 What happened was entering into the user code, the interrupts were enabled and a max interrupts off was recorded. The trace buffer was saved along with various information about the task: comm, pid, uid, priority, etc. The uid is recorded with task_uid(tsk). But this is a macro that uses rcu_read_lock() to retrieve the data, and this happened to happen where RCU is blind (user_enter). As only the preempt and irqs off tracers can have this happen, and they both only have the tsk == current, if tsk == current, use current_uid() instead of task_uid(), as current_uid() does not use RCU as only current can change its uid. This fixes the RCU suspicious splat. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
1 parent 0184d50
checkstack.pl
#!/usr/bin/perl
# Check the stack usage of functions
#
# Copyright Joern Engel <joern@lazybastard.org>
# Inspired by Linus Torvalds
# Original idea maybe from Keith Owens
# s390 port and big speedup by Arnd Bergmann <arnd@bergmann-dalldorf.de>
# Mips port by Juan Quintela <quintela@mandrakesoft.com>
# IA64 port via Andreas Dilger
# Arm port by Holger Schurig
# sh64 port by Paul Mundt
# Random bits by Matt Mackall <mpm@selenic.com>
# M68k port by Geert Uytterhoeven and Andreas Schwab
# AVR32 port by Haavard Skinnemoen (Atmel)
# PARISC port by Kyle McMartin <kyle@parisc-linux.org>
# sparc port by Martin Habets <errandir_news@mph.eclipse.co.uk>
#
# Usage:
# objdump -d vmlinux | scripts/checkstack.pl [arch]
#
# TODO : Port to all architectures (one regex per arch)
use strict;
# check for arch
#
# $re is used for two matches:
# $& (whole re) matches the complete objdump line with the stack growth
# $1 (first bracket) matches the size of the stack growth
#
# $dre is similar, but for dynamic stack redutions:
# $& (whole re) matches the complete objdump line with the stack growth
# $1 (first bracket) matches the dynamic amount of the stack growth
#
# use anything else and feel the pain ;)
my (@stack, $re, $dre, $x, $xs, $funcre);
{
my $arch = shift;
if ($arch eq "") {
$arch = `uname -m`;
chomp($arch);
}
$x = "[0-9a-f]"; # hex character
$xs = "[0-9a-f ]"; # hex character or space
$funcre = qr/^$x* <(.*)>:$/;
if ($arch eq 'arm') {
#c0008ffc: e24dd064 sub sp, sp, #100 ; 0x64
$re = qr/.*sub.*sp, sp, #(([0-9]{2}|[3-9])[0-9]{2})/o;
} elsif ($arch eq 'avr32') {
#8000008a: 20 1d sub sp,4
#80000ca8: fa cd 05 b0 sub sp,sp,1456
$re = qr/^.*sub.*sp.*,([0-9]{1,8})/o;
} elsif ($arch =~ /^i[3456]86$/) {
#c0105234: 81 ec ac 05 00 00 sub $0x5ac,%esp
$re = qr/^.*[as][du][db] \$(0x$x{1,8}),\%esp$/o;
$dre = qr/^.*[as][du][db] (%.*),\%esp$/o;
} elsif ($arch eq 'x86_64') {
# 2f60: 48 81 ec e8 05 00 00 sub $0x5e8,%rsp
$re = qr/^.*[as][du][db] \$(0x$x{1,8}),\%rsp$/o;
$dre = qr/^.*[as][du][db] (\%.*),\%rsp$/o;
} elsif ($arch eq 'ia64') {
#e0000000044011fc: 01 0f fc 8c adds r12=-384,r12
$re = qr/.*adds.*r12=-(([0-9]{2}|[3-9])[0-9]{2}),r12/o;
} elsif ($arch eq 'm68k') {
# 2b6c: 4e56 fb70 linkw %fp,#-1168
# 1df770: defc ffe4 addaw #-28,%sp
$re = qr/.*(?:linkw %fp,|addaw )#-([0-9]{1,4})(?:,%sp)?$/o;
} elsif ($arch eq 'metag') {
#400026fc: 40 00 00 82 ADD A0StP,A0StP,#0x8
$re = qr/.*ADD.*A0StP,A0StP,\#(0x$x{1,8})/o;
$funcre = qr/^$x* <[^\$](.*)>:$/;
} elsif ($arch eq 'mips64') {
#8800402c: 67bdfff0 daddiu sp,sp,-16
$re = qr/.*daddiu.*sp,sp,-(([0-9]{2}|[3-9])[0-9]{2})/o;
} elsif ($arch eq 'mips') {
#88003254: 27bdffe0 addiu sp,sp,-32
$re = qr/.*addiu.*sp,sp,-(([0-9]{2}|[3-9])[0-9]{2})/o;
} elsif ($arch eq 'parisc' || $arch eq 'parisc64') {
$re = qr/.*ldo ($x{1,8})\(sp\),sp/o;
} elsif ($arch eq 'ppc') {
#c00029f4: 94 21 ff 30 stwu r1,-208(r1)
$re = qr/.*stwu.*r1,-($x{1,8})\(r1\)/o;
} elsif ($arch eq 'ppc64') {
#XXX
$re = qr/.*stdu.*r1,-($x{1,8})\(r1\)/o;
} elsif ($arch eq 'powerpc') {
$re = qr/.*st[dw]u.*r1,-($x{1,8})\(r1\)/o;
} elsif ($arch =~ /^s390x?$/) {
# 11160: a7 fb ff 60 aghi %r15,-160
# or
# 100092: e3 f0 ff c8 ff 71 lay %r15,-56(%r15)
$re = qr/.*(?:lay|ag?hi).*\%r15,-(([0-9]{2}|[3-9])[0-9]{2})
(?:\(\%r15\))?$/ox;
} elsif ($arch =~ /^sh64$/) {
#XXX: we only check for the immediate case presently,
# though we will want to check for the movi/sub
# pair for larger users. -- PFM.
#a00048e0: d4fc40f0 addi.l r15,-240,r15
$re = qr/.*addi\.l.*r15,-(([0-9]{2}|[3-9])[0-9]{2}),r15/o;
} elsif ($arch =~ /^blackfin$/) {
# 0: 00 e8 38 01 LINK 0x4e0;
$re = qr/.*[[:space:]]LINK[[:space:]]*(0x$x{1,8})/o;
} elsif ($arch eq 'sparc' || $arch eq 'sparc64') {
# f0019d10: 9d e3 bf 90 save %sp, -112, %sp
$re = qr/.*save.*%sp, -(([0-9]{2}|[3-9])[0-9]{2}), %sp/o;
} else {
print("wrong or unknown architecture \"$arch\"\n");
exit
}
}
#
# main()
#
my ($func, $file, $lastslash);
while (my $line = <STDIN>) {
if ($line =~ m/$funcre/) {
$func = $1;
}
elsif ($line =~ m/(.*):\s*file format/) {
$file = $1;
$file =~ s/\.ko//;
$lastslash = rindex($file, "/");
if ($lastslash != -1) {
$file = substr($file, $lastslash + 1);
}
}
elsif ($line =~ m/$re/) {
my $size = $1;
$size = hex($size) if ($size =~ /^0x/);
if ($size > 0xf0000000) {
$size = - $size;
$size += 0x80000000;
$size += 0x80000000;
}
next if ($size > 0x10000000);
next if $line !~ m/^($xs*)/;
my $addr = $1;
$addr =~ s/ /0/g;
$addr = "0x$addr";
my $intro = "$addr $func [$file]:";
my $padlen = 56 - length($intro);
while ($padlen > 0) {
$intro .= ' ';
$padlen -= 8;
}
next if ($size < 100);
push @stack, "$intro$size\n";
}
elsif (defined $dre && $line =~ m/$dre/) {
my $size = "Dynamic ($1)";
next if $line !~ m/^($xs*)/;
my $addr = $1;
$addr =~ s/ /0/g;
$addr = "0x$addr";
my $intro = "$addr $func [$file]:";
my $padlen = 56 - length($intro);
while ($padlen > 0) {
$intro .= ' ';
$padlen -= 8;
}
push @stack, "$intro$size\n";
}
}
# Sort output by size (last field)
print sort { ($b =~ /:\t*(\d+)$/)[0] <=> ($a =~ /:\t*(\d+)$/)[0] } @stack;
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