[lttng-dev] [PATCH lttng-tools] Load modules through kmod

[Simon Marchi]

On 3 September 2014 15:10, David Goulet <dgoulet at efficios.com> wrote:
> On 26 Aug (16:27:46), Umut Tezduyar Lindskog wrote:
>> Instead of forking processes, load modules through libkmod.
>>
>> This adds a package dependency to kmod but can be disabled
>> by --disable-kmod option in ./configure.
>
> First, thanks for this patch, this is really good to have!
>
> Adding a dependency on libkmod might needs a bit more discussion for
> 2.6 which I'm quite open to that but I don't want to make the decision
> alone.
>
> So could we for now simply use a "--enable-kmod" and by default disable
> it? If we decide to depend on libkmod, should be quite easy to revert
> back to --disable-kmod.

Actually, the default should be to use kmod if it is found, revert to
modprobe otherwise.

> Thanks!
> David
>
>>
>> The startup time has decreased by %36 on our embedded mips
>> product. The measurement is done by cgroup cpu shares.
>> ---
>>  configure.ac                      |   34 ++++++++++++++++++++++++
>>  src/bin/lttng-sessiond/modprobe.c |   53 +++++++++++++++++++++++++++++++++++++
>>  2 files changed, 87 insertions(+)
>>
>> diff --git a/configure.ac b/configure.ac
>> index a8e04f5..b36a95d 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -200,6 +200,32 @@ AC_CHECK_DECL([cmm_smp_mb__before_uatomic_or], [],
>>          [AC_MSG_ERROR([liburcu $liburcu_version or newer is needed])], [[#include <urcu.h>]]
>>  )
>>
>> +# Check kmod library
>> +AC_ARG_WITH(kmod-prefix,
>> +  AS_HELP_STRING([--with-kmod-prefix=PATH],
>> +                 [Specify the installation prefix of the kmod library.
>> +               Headers must be in PATH/include; libraries in PATH/lib.]),
>> +               [
>> +                 CPPFLAGS="$CPPFLAGS -I${withval}/include"
>> +                 LDFLAGS="$LDFLAGS -L${withval}/lib64 -L${withval}/lib"
>> +               ])
>> +
>> +AC_ARG_ENABLE(kmod,
>> +     AS_HELP_STRING([--disable-kmod],[build without kmod support]),
>> +     kmod_support=$enableval, kmod_support=yes)
>> +
>> +AS_IF([test "x$kmod_support" = "xyes"], [
>> +     AC_CHECK_LIB([kmod], [kmod_module_probe_insert_module],
>> +             [
>> +                     AC_DEFINE([HAVE_KMOD], [1], [has kmod support])
>> +                     LIBS="$LIBS -lkmod"
>> +                     kmod_found=yes
>> +             ],
>> +             [AC_MSG_ERROR([Cannot find kmod >= 5. Use --with-kmod-prefix=PREFIX to specify its location, or specify --disable-kmod to build lttng-tools without kmod support.])]
>> +     )
>> +])
>> +AM_CONDITIONAL([HAVE_KMOD], [test "x$kmod_found" = xyes])
>> +
>>  AC_ARG_WITH(lttng-ust-prefix,
>>    AS_HELP_STRING([--with-lttng-ust-prefix=PATH],
>>                   [Specify the installation prefix of the lttng-ust library.
>> @@ -483,6 +509,14 @@ done
>>  AS_ECHO_N("Target architecture: ")
>>  AS_ECHO($target_arch)
>>
>> +# kmod enabled/disabled
>> +AS_ECHO_N("kmod support: ")
>> +AS_IF([test "x$kmod_support" = "xyes"],[
>> +     AS_ECHO("Enabled")
>> +],[
>> +     AS_ECHO("Disabled")
>> +])
>> +
>>  # LTTng-UST enabled/disabled
>>  AS_ECHO_N("Lttng-UST support: ")
>>  AS_IF([test "x$lttng_ust_support" = "xyes"],[
>> diff --git a/src/bin/lttng-sessiond/modprobe.c b/src/bin/lttng-sessiond/modprobe.c
>> index 3cc67f0..40a2ee0 100644
>> --- a/src/bin/lttng-sessiond/modprobe.c
>> +++ b/src/bin/lttng-sessiond/modprobe.c
>> @@ -164,6 +164,58 @@ void modprobe_remove_lttng_all(void)
>>       modprobe_remove_lttng_control();
>>  }
>>
>> +#if HAVE_KMOD
>> +#include <libkmod.h>
>> +static void log_kmod(void *data, int priority, const char *file, int line,
>> +                  const char *fn, const char *format, va_list args)
>> +{
>> +     char *str;
>> +     if (vasprintf(&str, format, args) < 0)
>> +             return;
>> +     DBG("libkmod: %s", str);
>> +     free(str);
>> +}
>> +static int modprobe_lttng(struct kern_modules_param *modules,
>> +                       int entries, int required)
>> +{
>> +     int ret = 0, i;
>> +     struct kmod_ctx *ctx;
>> +
>> +     ctx = kmod_new(NULL, NULL);
>> +     if (!ctx) {
>> +             PERROR("Unable to create kmod library context");
>> +             ret = -ENOMEM;
>> +             goto error;
>> +     }
>> +
>> +     kmod_set_log_fn(ctx, log_kmod, NULL);
>> +     kmod_load_resources(ctx);
>> +
>> +     for (i = 0; i < entries; i++) {
>> +             struct kmod_module *mod = NULL;
>> +
>> +             ret = kmod_module_new_from_name(ctx, modules[i].name, &mod);
>> +             if (ret < 0) {
>> +                     PERROR("Failed to create kmod module for %s", modules[i].name);
>> +                     goto error;
>> +             }
>> +
>> +             ret = kmod_module_probe_insert_module(mod, KMOD_PROBE_IGNORE_LOADED, NULL, NULL, NULL, NULL);
>> +             if (required && ret < 0) {
>> +                     ERR("Unable to load module %s", modules[i].name);
>> +             } else {
>> +                     DBG("Modprobe successfully %s", modules[i].name);
>> +             }
>> +
>> +             kmod_module_unref(mod);
>> +     }
>> +
>> +error:
>> +     if (ctx)
>> +             kmod_unref(ctx);
>> +     return ret;
>> +}
>> +#else
>>  static int modprobe_lttng(struct kern_modules_param *modules,
>>                         int entries, int required)
>>  {
>> @@ -194,6 +246,7 @@ static int modprobe_lttng(struct kern_modules_param *modules,
>>  error:
>>       return ret;
>>  }
>> +#endif
>>
>>  /*
>>   * Load control kernel module(s).
>> --
>> 1.7.10.4
>>
>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
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