Date: Sat, 21 Mar 2015 05:43:43 +0100 From: Mateusz Guzik <mjguzik@gmail.com> To: Tiwei Bie <btw@mail.ustc.edu.cn> Cc: Konstantin Belousov <kostikbel@gmail.com>, freebsd-hackers@freebsd.org, Prasad Joshi <prasadjoshi.linux@gmail.com> Subject: Re: [PATCH] Finish the task 'Fix corefilename race' Message-ID: <20150321044343.GD27736@dft-labs.eu> In-Reply-To: <20150320063604.GA69307@freebsd> References: <1426749223-18118-1-git-send-email-btw@mail.ustc.edu.cn> <20150319101019.GZ2379@kib.kiev.ua> <20150319113530.GA33176@freebsd> <20150319144004.GD2379@kib.kiev.ua> <20150320000418.GA78913@freebsd> <CALJbWeotyhiGVkruF-mpPNM0DBSZt9bjD4RdhZZrzv-3jwP0ag@mail.gmail.com> <20150320063604.GA69307@freebsd>
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On Fri, Mar 20, 2015 at 02:36:04PM +0800, Tiwei Bie wrote:
> On Fri, Mar 20, 2015 at 11:18:27AM +0530, Prasad Joshi wrote:
> > On Fri, Mar 20, 2015 at 5:34 AM, Tiwei Bie <btw@mail.ustc.edu.cn> wrote:
> > > On Thu, Mar 19, 2015 at 04:40:04PM +0200, Konstantin Belousov wrote:
> > >> On Thu, Mar 19, 2015 at 07:35:30PM +0800, Tiwei Bie wrote:
> > >> > On Thu, Mar 19, 2015 at 12:10:19PM +0200, Konstantin Belousov wrote:
> > >> > > On Thu, Mar 19, 2015 at 03:13:43PM +0800, Tiwei Bie wrote:
> > >> > > > Hi, Mateusz!
> > >> > > >
> > >> > > > I have finished the task: Fix corefilename race [1].
> > >> > > >
> > >> > > > Following is my patch:
> > >> > > >
> > >> > > > ---
> > >> > > > sys/kern/kern_sig.c | 22 ++++++++++++++++++++--
> > >> > > > 1 file changed, 20 insertions(+), 2 deletions(-)
> > >> > > >
> > >> > > > diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
> > >> > > > index 58d9707..a1421cb 100644
> > >> > > > --- a/sys/kern/kern_sig.c
> > >> > > > +++ b/sys/kern/kern_sig.c
> > >> > > > @@ -3090,8 +3090,24 @@ static int compress_user_cores = 0;
> > >> > > > #endif
> > >> > > >
> > >> > > > static char corefilename[MAXPATHLEN] = {"%N.core"};
> > >> > > > -SYSCTL_STRING(_kern, OID_AUTO, corefile, CTLFLAG_RWTUN, corefilename,
> > >> > > > - sizeof(corefilename), "Process corefile name format string");
> > >> > > > +
> > >> > > > +static struct sx corefilename_lock;
> > >> > > > +SX_SYSINIT(corefilename_init, &corefilename_lock, "corefilename lock");
> > >> > > > +
> > >> > > > +static int
> > >> > > > +sysctl_kern_corefile(SYSCTL_HANDLER_ARGS)
> > >> > > > +{
> > >> > > > + int error;
> > >> > > > +
> > >> > > > + sx_xlock(&corefilename_lock);
> > >> > > > + error = sysctl_handle_string(oidp, corefilename, MAXPATHLEN, req);
> >
> > Hello,
> >
> > Though I am not an expert FreeBSD developer. In my humble opinion,
> > MAXPATHLEN must be replaced with sizeof(corefilename). For example,
> > the SYSCTL_STRING line (above) removed in this patch, preferred to use
> > sizeof(corefilename) instead of MAXPATHLEN.
> >
>
> Because corefilename is defined as `char corefilename[MAXPATHLEN]',
> sizeof(corefilename) equals MAXPATHLEN. So, technically speaking,
> both of them are right. But one of them may be preferred to keep the
> coding style consistent. I also think sizeof(corefilename) is a
> better choice. Thanks for pointing it out, I updated my patch:
>
> ---
> sys/kern/kern_sig.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
> index 58d9707..8410d9d 100644
> --- a/sys/kern/kern_sig.c
> +++ b/sys/kern/kern_sig.c
> @@ -3089,9 +3089,28 @@ SYSCTL_INT(_kern, OID_AUTO, compress_user_cores_gzlevel, CTLFLAG_RWTUN,
> static int compress_user_cores = 0;
> #endif
>
> +/*
> + * Protect the access to corefilename[] by allproc_lock.
> + */
> +#define corefilename_lock allproc_lock
> +
> static char corefilename[MAXPATHLEN] = {"%N.core"};
> -SYSCTL_STRING(_kern, OID_AUTO, corefile, CTLFLAG_RWTUN, corefilename,
> - sizeof(corefilename), "Process corefile name format string");
> +
> +static int
> +sysctl_kern_corefile(SYSCTL_HANDLER_ARGS)
> +{
> + int error;
> +
> + sx_xlock(&corefilename_lock);
> + error = sysctl_handle_string(oidp, corefilename, sizeof(corefilename),
> + req);
> + sx_xunlock(&corefilename_lock);
> +
> + return (error);
> +}
> +SYSCTL_PROC(_kern, OID_AUTO, corefile, CTLTYPE_STRING | CTLFLAG_RWTUN |
> + CTLFLAG_MPSAFE, 0, 0, sysctl_kern_corefile, "A",
> + "Process corefile name format string");
>
> /*
> * corefile_open(comm, uid, pid, td, compress, vpp, namep)
> @@ -3120,6 +3139,7 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
> name = malloc(MAXPATHLEN, M_TEMP, M_WAITOK | M_ZERO);
> indexpos = -1;
> (void)sbuf_new(&sb, name, MAXPATHLEN, SBUF_FIXEDLEN);
> + sx_slock(&corefilename_lock);
> for (i = 0; format[i] != '\0'; i++) {
> switch (format[i]) {
> case '%': /* Format character */
> @@ -3162,6 +3182,7 @@ corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
> break;
> }
> }
> + sx_sunlock(&corefilename_lock);
> free(hostname, M_TEMP);
> if (compress)
> sbuf_printf(&sb, GZ_SUFFIX);
>
Thanks, committed as r280312.
--
Mateusz Guzik <mjguzik gmail.com>
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