7:54 a.m.
On 5/30/2019 5:03 PM, Dave Anderson wrote:
----- Original Message -----
> Hi Dave,
>
> I don't know why this difference arises, but with certain kernel configurations,
> the source file and line information of the schedule() function becomes the
> following, not "/kernel/sched/core.c".
>
> crash> sym schedule
> ffffffffab0d3666 (T) schedule
> /share/src/linux-5.0.1/./arch/x86/include/asm/current.h: 15
Yeah, presumably happens because your kernel doesn't have the ftrace nop compiled
into the beginning of each function. When it does, the first address in the
schedule function would be in kernel/sched/core.c:
crash> sym schedule
ffffffffa22b5dc0 (T) schedule
/usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/kernel/sched/core.c:
3503
crash> dis -l schedule
/usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/kernel/sched/core.c:
3503
0xffffffffa22b5dc0 <schedule>: nopl 0x0(%rax,%rax,1) [FTRACE NOP]
/usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/./arch/x86/include/asm/current.h:
15
0xffffffffa22b5dc5 <schedule+5>: push %rbx
0xffffffffa22b5dc6 <schedule+6>: mov %gs:0x15f00,%rbx
/usr/src/debug/kernel-5.2.0-0.rc2.1.elrdy/linux-5.2.0-0.rc2.1.elrdy.x86_64/kernel/sched/core.c:
3506
0xffffffffa22b5dcf <schedule+15>: mov 0x10(%rbx),%rax
0xffffffffa22b5dd3 <schedule+19>: test %rax,%rax
0xffffffffa22b5dd6 <schedule+22>: je 0xffffffffa22b5de2
<schedule+34>
...
Ah, I see. Thanks! I think it is CONFIG_DYNAMIC_FTRACE,
which the config does not have.
$ grep FTRACE config-5.0.1
CONFIG_HAVE_KPROBES_ON_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_REGS=y
CONFIG_HAVE_FTRACE_MCOUNT_RECORD=y
CONFIG_FTRACE=y
# CONFIG_FTRACE_SYSCALLS is not set
# CONFIG_FTRACE_STARTUP_TEST is not set
Thanks,
Kazu
If ftrace is not enabled, then it would show asm/current.h because the first instruction
in schedule() is the evaluation of "current":
asmlinkage __visible void __sched schedule(void)
{
struct task_struct *tsk = current;
which is #define'd in asm/current.h:
#define get_current() (current_thread_info()->task)
#define current get_current()
Anyway, I'll take a look and test the patch tomorrow.
Thanks,
Dave
>
> This causes the "sys -c" option not to print the information of system
calls,
> and makes it very slow.
>
> crash> sys -c | sh -c 'time cat'
> NUM SYSTEM CALL FILE AND LINE NUMBER
> 0 __x64_sys_read
> 1 __x64_sys_write
> 2 __x64_sys_open
> ...
> 333 __x64_sys_io_pgetevents
> 334 __x64_sys_rseq
>
> real 2m32.669s
> user 0m0.002s
> sys 0m0.022s
>
> With this patch, the option can print the information in not too long time:
>
> crash> sys -c | sh -c 'time cat'
> NUM SYSTEM CALL FILE AND LINE NUMBER
> 0 __x64_sys_read ../fs/read_write.c: 588
> 1 __x64_sys_write ../fs/read_write.c: 610
> 2 __x64_sys_open ../fs/open.c: 1079
> ...
> 333 __x64_sys_io_pgetevents ../fs/aio.c: 2139
> 334 __x64_sys_rseq ../kernel/rseq.c: 308
>
> real 0m10.905s
> user 0m0.000s
> sys 0m0.024s
>
> Also, in dump_sys_call_table(), it looks like there is no need to call
> get_build_directory() for each system call, so moving it out of the loop
> makes it faster.
>
> [without moving the get_build_directory()]
> real 0m15.862s
> user 0m0.003s
> sys 0m0.020s
>
> Signed-off-by: Kazuhito Hagio <k-hagio(a)ab.jp.nec.com>
> ---
> kernel.c | 2 +-
> symbols.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel.c b/kernel.c
> index db25f22e4ec6..22909d28cefc 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -5679,6 +5679,7 @@ dump_sys_call_table(char *spec, int cnt)
>
> fprintf(fp, "%s", sys_call_hdr);
>
> + get_build_directory(buf2);
> for (i = 0, sct = sys_call_table; i < NR_syscalls; i++, sct++) {
> if (!(scp = value_symbol(*sct))) {
> if (confirmed || CRASHDEBUG(1)) {
> @@ -5710,7 +5711,6 @@ dump_sys_call_table(char *spec, int cnt)
> */
> sp = value_search(*sct, NULL);
> spn = next_symbol(NULL, sp);
> - get_build_directory(buf2);
>
> for (addr = *sct; sp && spn && (addr < spn->value); addr++)
{
> BZERO(buf1, BUFSIZE);
> diff --git a/symbols.c b/symbols.c
> index 863d1f0a8e25..3ce8692fd397 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -4296,7 +4296,7 @@ get_build_directory(char *buf)
> get_line_number(symbol_value("do_schedule"), buf, FALSE);
> else
> return NULL;
> - if ((p = strstr(buf, "/kernel/")))
> + if ((p = strstr(buf, "/kernel/")) || (p = strstr(buf,
"/./arch/")))
> *p = NULLCHAR;
> else
> return(NULL);
> --
> 2.18.1
>
--
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