Incorrect cv_wait_sig() return values?
Hi,
I recently noticed that cv_wait_sig() will return -1
rather than EINTR when a SIGINT is delivered. This is
in contrast to CONDVAR(9) which states:
<...>
cv_wait_sig() and cv_timedwait_sig() return prematurely with a
value of EINTR or ERESTART if a signal is caught
<...>
To demonstrate the problem outside my out-of-tree driver, I
took the skeleton driver from
http://www.captain.at/programming/freebsd/
and added the following function, invoked at module
load:
static struct mtx m;
static struct cv c;
static void
cv_test(void)
{
int rc;
mtx_init(&m, "skel_m", MTX_DEF, MTX_DEF);
cv_init(&c, "skel_c");
mtx_lock(&m);
rc = cv_wait_sig(&c, &m);
mtx_unlock(&m);
printf("cv_wait_sig returned %d\n", rc);
cv_destroy(&c);
mtx_destroy(&m);
}
I load the module, and I ^C kldload after a few seconds
to break out of the cv_wait_sig(), which results in this
output on console:
Skeleton KLD loaded.
cv_wait_sig returned -1
Am I doing something wrong, or are condvars broken?
I've tried to track this down with dtrace, but failed..
Thanks,
Drew
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Re: Incorrect cv_wait_sig() return values?
On Wed, Aug 04, 2010 at 10:36:24AM -0400, Andrew Gallatin wrote:
> Hi,
>
> I recently noticed that cv_wait_sig() will return -1
> rather than EINTR when a SIGINT is delivered. This is
> in contrast to CONDVAR(9) which states:
>
> <...>
> cv_wait_sig() and cv_timedwait_sig() return prematurely with a
> value of EINTR or ERESTART if a signal is caught
> <...>
>
> To demonstrate the problem outside my out-of-tree driver, I
> took the skeleton driver from
> http://www.captain.at/programming/freebsd/
> and added the following function, invoked at module
> load:
>
> static struct mtx m;
> static struct cv c;
>
> static void
> cv_test(void)
> {
> int rc;
>
> mtx_init(&m, "skel_m", MTX_DEF, MTX_DEF);
> cv_init(&c, "skel_c");
> mtx_lock(&m);
> rc = cv_wait_sig(&c, &m);
> mtx_unlock(&m);
> printf("cv_wait_sig returned %d\n", rc);
> cv_destroy(&c);
> mtx_destroy(&m);
> }
>
>
> I load the module, and I ^C kldload after a few seconds
> to break out of the cv_wait_sig(), which results in this
> output on console:
>
> Skeleton KLD loaded.
> cv_wait_sig returned -1
>
> Am I doing something wrong, or are condvars broken?
> I've tried to track this down with dtrace, but failed..
What version of the system do you use ? I cannot confirm this on
the HEAD from several hours ago with the following test module.
On the SIGINT I get `4' printed, which is EINTR.
#include
#include
#include
#include
#include
#include
#include
static struct mtx m;
static struct cv c;
static void
cv_test(void)
{
int rc;
mtx_init(&m, "skel_m", MTX_DEF, MTX_DEF);
cv_init(&c, "skel_c");
mtx_lock(&m);
rc = cv_wait_sig(&c, &m);
mtx_unlock(&m);
printf("cv_wait_sig returned %d\n", rc);
cv_destroy(&c);
mtx_destroy(&m);
}
static int
test_load(module_t mod, int cmd, void *arg)
{
switch (cmd) {
case MOD_LOAD:
cv_test();
break;
}
return (0);
}
static moduledata_t test_module = {
"test",
&test_load,
NULL
};
DECLARE_MODULE(test, test_module, SI_SUB_KLD, SI_ORDER_FIRST);
MODULE_VERSION(test, 1);
pgpz2cxfxk5ZS.pgp
Description: PGP signature
Re: Incorrect cv_wait_sig() return values?
On Wed, Aug 04, 2010 at 06:46:04PM +0300, Kostik Belousov wrote:
> On Wed, Aug 04, 2010 at 10:36:24AM -0400, Andrew Gallatin wrote:
> > Hi,
> >
> > I recently noticed that cv_wait_sig() will return -1
> > rather than EINTR when a SIGINT is delivered. This is
> > in contrast to CONDVAR(9) which states:
> >
> > <...>
> > cv_wait_sig() and cv_timedwait_sig() return prematurely with a
> > value of EINTR or ERESTART if a signal is caught
> > <...>
> >
> > To demonstrate the problem outside my out-of-tree driver, I
> > took the skeleton driver from
> > http://www.captain.at/programming/freebsd/
> > and added the following function, invoked at module
> > load:
> >
> > static struct mtx m;
> > static struct cv c;
> >
> > static void
> > cv_test(void)
> > {
> > int rc;
> >
> > mtx_init(&m, "skel_m", MTX_DEF, MTX_DEF);
> > cv_init(&c, "skel_c");
> > mtx_lock(&m);
> > rc = cv_wait_sig(&c, &m);
> > mtx_unlock(&m);
> > printf("cv_wait_sig returned %d\n", rc);
> > cv_destroy(&c);
> > mtx_destroy(&m);
> > }
> >
> >
> > I load the module, and I ^C kldload after a few seconds
> > to break out of the cv_wait_sig(), which results in this
> > output on console:
> >
> > Skeleton KLD loaded.
> > cv_wait_sig returned -1
> >
> > Am I doing something wrong, or are condvars broken?
> > I've tried to track this down with dtrace, but failed..
>
> What version of the system do you use ? I cannot confirm this on
> the HEAD from several hours ago with the following test module.
> On the SIGINT I get `4' printed, which is EINTR.
BTW, -1 is ERESTART, so if you have SIGINT catched with SA_RESTART
flag in the process that initiated kldload(2) syscall, then -1
is the right return code for cv_wait_sig.
pgp9l3SKbjafV.pgp
Description: PGP signature
Re: Incorrect cv_wait_sig() return values?
Kostik Belousov wrote: BTW, -1 is ERESTART, so if you have SIGINT catched with SA_RESTART flag in the process that initiated kldload(2) syscall, then -1 is the right return code for cv_wait_sig. Ah, makes sense. I hadn't considered that a BSD kernel error could be negative. I should have actually looked at errno.h. Sorry for the noise, and thanks for the explanation. Drew ___ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
