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Message-Id: <20121219151243.9f8882c8.akpm@linux-foundation.org> Date: Wed, 19 Dec 2012 15:12:43 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: "Dae S. Kim" <dae@...atum.com> Cc: arnd@...db.de, gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] char/misc.c: misc_register: Do not loop on misc_list unconditionally On Mon, 17 Dec 2012 23:26:38 +0100 "Dae S. Kim" <dae@...atum.com> wrote: > If the minor number is assigned dynamically, there is no need to > search for misc->minor in misc_list, since misc->minor == > MISC_DYNAMIC_MINOR. > > ... > > --- a/drivers/char/misc.c > +++ b/drivers/char/misc.c > @@ -190,12 +190,6 @@ int misc_register(struct miscdevice * misc) > INIT_LIST_HEAD(&misc->list); > > mutex_lock(&misc_mtx); > - list_for_each_entry(c, &misc_list, list) { > - if (c->minor == misc->minor) { > - mutex_unlock(&misc_mtx); > - return -EBUSY; > - } > - } > > if (misc->minor == MISC_DYNAMIC_MINOR) { > int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS); > @@ -205,6 +199,13 @@ int misc_register(struct miscdevice * misc) > } > misc->minor = DYNAMIC_MINORS - i - 1; > set_bit(i, misc_minors); > + } else { > + list_for_each_entry(c, &misc_list, list) { > + if (c->minor == misc->minor) { > + mutex_unlock(&misc_mtx); > + return -EBUSY; > + } > + } > } > Looks OK. It permits this: From: Andrew Morton <akpm@...ux-foundation.org> Subject: drivers-char-miscc-misc_register-do-not-loop-on-misc_list-unconditionally-fix reduce scope of local `c' Cc: "Dae S. Kim" <dae@...atum.com> Cc: Arnd Bergmann <arnd@...db.de> Cc: Dae S. Kim <dae@...atum.com> Cc: Greg KH <greg@...ah.com> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org> --- drivers/char/misc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff -puN drivers/char/misc.c~drivers-char-miscc-misc_register-do-not-loop-on-misc_list-unconditionally-fix drivers/char/misc.c --- a/drivers/char/misc.c~drivers-char-miscc-misc_register-do-not-loop-on-misc_list-unconditionally-fix +++ a/drivers/char/misc.c @@ -183,7 +183,6 @@ static const struct file_operations misc int misc_register(struct miscdevice * misc) { - struct miscdevice *c; dev_t dev; int err = 0; @@ -200,6 +199,8 @@ int misc_register(struct miscdevice * mi misc->minor = DYNAMIC_MINORS - i - 1; set_bit(i, misc_minors); } else { + struct miscdevice *c; + list_for_each_entry(c, &misc_list, list) { if (c->minor == misc->minor) { mutex_unlock(&misc_mtx); _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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