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path: root/tools/perf/scripts/perl/failed-syscalls.pl
blob: 55e7ae4c5c88707e44d90270c2a7fc4b1546c459 (plain)
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# failed system call counts
# (c) 2010, Tom Zanussi <tzanussi@gmail.com>
# Licensed under the terms of the GNU GPL License version 2
#
# Displays system-wide failed system call totals
# If a [comm] arg is specified, only syscalls called by [comm] are displayed.

use lib "$ENV{'PERF_EXEC_PATH'}/scripts/perl/Perf-Trace-Util/lib";
use lib "./Perf-Trace-Util/lib";
use Perf::Trace::Core;
use Perf::Trace::Context;
use Perf::Trace::Util;

my $for_comm = shift;

my %failed_syscalls;

sub raw_syscalls::sys_exit
{
	my ($event_name, $context, $common_cpu, $common_secs, $common_nsecs,
	    $common_pid, $common_comm,
	    $id, $ret) = @_;

	if ($ret < 0) {
	    $failed_syscalls{$common_comm}++;
	}
}

sub syscalls::sys_exit
{
	raw_syscalls::sys_exit(@_)
}

sub trace_end
{
    printf("\nfailed syscalls by comm:\n\n");

    printf("%-20s  %10s\n", "comm", "# errors");
    printf("%-20s  %6s  %10s\n", "--------------------", "----------");

    foreach my $comm (sort {$failed_syscalls{$b} <=> $failed_syscalls{$a}}
		      keys %failed_syscalls) {
	next if ($for_comm && $comm ne $for_comm);

	printf("%-20s  %10s\n", $comm, $failed_syscalls{$comm});
    }
}
/div>
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'sound/soc/davinci/davinci-i2s.c')