Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752845AbZKPMFu (ORCPT ); Mon, 16 Nov 2009 07:05:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752763AbZKPMFu (ORCPT ); Mon, 16 Nov 2009 07:05:50 -0500 Received: from www84.your-server.de ([213.133.104.84]:49442 "EHLO www84.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447AbZKPMFt (ORCPT ); Mon, 16 Nov 2009 07:05:49 -0500 Subject: Re: [PATCH 6/7] kfifo: add kfifo_skip, kfifo_from_user and kfifo_to_user From: Stefani Seibold To: linux-kernel Cc: Andrew Morton , Arnd Bergmann , Andi Kleen , Amerigo Wang , Joe Perches In-Reply-To: <1258372242.31356.1.camel@wall-e> References: <1258372242.31356.1.camel@wall-e> Content-Type: text/plain; charset="ISO-8859-15" Date: Mon, 16 Nov 2009 13:05:54 +0100 Message-ID: <1258373154.31356.18.camel@wall-e> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit X-Authenticated-Sender: stefani@seibold.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8236 Lines: 283 Add kfifo_reset_out() to lockless save discard the fifo output Add kfifo_skip() to skip a number of output bytes Add kfifo_from_user() to copy user space data into the fifo Add kfifo_to_user() to copy fifo data to user space Signed-off-by: Stefani Seibold Acked-by: Greg Kroah-Hartman Acked-by: Mauro Carvalho Chehab Acked-by: Andi Kleen Acked-by: Arnd Bergmann --- include/linux/kfifo.h | 47 ++++++++++++++++ kernel/kfifo.c | 139 ++++++++++++++++++++++++++++++++++++++++++++------ 2 files changed, 170 insertions(+), 16 deletions(-) diff -u -N -r kfifo5/include/linux/kfifo.h kfifo6/include/linux/kfifo.h --- kfifo5/include/linux/kfifo.h 2009-10-19 21:25:25.000000000 +0200 +++ kfifo6/include/linux/kfifo.h 2009-10-19 21:29:14.000000000 +0200 @@ -122,6 +122,16 @@ } /** + * kfifo_reset_out - skip FIFO contents + * @fifo: the fifo to be emptied. + */ +static inline void kfifo_reset_out(struct kfifo *fifo) +{ + smp_mb(); + fifo->out = fifo->in; +} + +/** * kfifo_size - returns the size of the fifo in bytes * @fifo: the fifo to be used. */ @@ -228,4 +238,41 @@ return ret; } +extern void kfifo_skip(struct kfifo *fifo, unsigned int len); + +extern __must_check unsigned int kfifo_from_user(struct kfifo *fifo, + const void __user *from, unsigned int n); + +extern __must_check unsigned int kfifo_to_user(struct kfifo *fifo, + void __user *to, unsigned int n); + +/** + * __kfifo_add_out internal helper function for updating the out offset + */ +static inline void __kfifo_add_out(struct kfifo *fifo, + unsigned int off) +{ + smp_mb(); + fifo->out += off; +} + +/** + * __kfifo_add_in internal helper function for updating the in offset + */ +static inline void __kfifo_add_in(struct kfifo *fifo, + unsigned int off) +{ + smp_wmb(); + fifo->in += off; +} + +/** + * __kfifo_off internal helper function for calculating the index of a + * given offeset + */ +static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off) +{ + return off & (fifo->size - 1); +} + #endif diff -u -N -r kfifo5/kernel/kfifo.c kfifo6/kernel/kfifo.c --- kfifo5/kernel/kfifo.c 2009-10-19 21:25:25.000000000 +0200 +++ kfifo6/kernel/kfifo.c 2009-10-19 21:29:14.000000000 +0200 @@ -26,6 +26,7 @@ #include #include #include +#include static void _kfifo_init(struct kfifo *fifo, unsigned char *buffer, unsigned int size) @@ -100,6 +101,21 @@ EXPORT_SYMBOL(kfifo_free); /** + * kfifo_skip - skip output data + * @fifo: the fifo to be used. + * @len: number of bytes to skip + */ +void kfifo_skip(struct kfifo *fifo, unsigned int len) +{ + if (len < kfifo_len(fifo)) { + __kfifo_add_out(fifo, len); + return; + } + kfifo_reset_out(fifo); +} +EXPORT_SYMBOL(kfifo_skip); + +/** * kfifo_in - puts some data into the FIFO * @fifo: the fifo to be used. * @from: the data to be added. @@ -115,6 +131,7 @@ unsigned int kfifo_in(struct kfifo *fifo, const unsigned char *from, unsigned int len) { + unsigned int off; unsigned int l; len = min(len, fifo->size - fifo->in + fifo->out); @@ -126,21 +143,16 @@ smp_mb(); + off = __kfifo_off(fifo, fifo->in); + /* first put the data starting from fifo->in to buffer end */ - l = min(len, fifo->size - (fifo->in & (fifo->size - 1))); - memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), from, l); + l = min(len, fifo->size - off); + memcpy(fifo->buffer + off, from, l); /* then put the rest (if any) at the beginning of the buffer */ memcpy(fifo->buffer, from + l, len - l); - /* - * Ensure that we add the bytes to the kfifo -before- - * we update the fifo->in index. - */ - - smp_wmb(); - - fifo->in += len; + __kfifo_add_in(fifo, len); return len; } @@ -161,6 +173,7 @@ unsigned int kfifo_out(struct kfifo *fifo, unsigned char *to, unsigned int len) { + unsigned int off; unsigned int l; len = min(len, fifo->in - fifo->out); @@ -172,22 +185,116 @@ smp_rmb(); + off = __kfifo_off(fifo, fifo->out); + /* first get the data from fifo->out until the end of the buffer */ - l = min(len, fifo->size - (fifo->out & (fifo->size - 1))); - memcpy(to, fifo->buffer + (fifo->out & (fifo->size - 1)), l); + l = min(len, fifo->size - off); + memcpy(to, fifo->buffer + off, l); /* then get the rest (if any) from the beginning of the buffer */ memcpy(to + l, fifo->buffer, len - l); + __kfifo_add_out(fifo, len); + + return len; +} +EXPORT_SYMBOL(kfifo_out); + +/** + * kfifo_from_user - puts some data from user space into the FIFO + * @fifo: the fifo to be used. + * @from: pointer to the data to be added. + * @len: the length of the data to be added. + * + * This function copies at most @len bytes from the @from into the + * FIFO depending and returns the number of copied bytes. + * + * Note that with only one concurrent reader and one concurrent + * writer, you don't need extra locking to use these functions. + */ +unsigned int kfifo_from_user(struct kfifo *fifo, + const void __user *from, unsigned int len) +{ + unsigned int off; + unsigned int l; + int ret; + + len = min(len, fifo->size - fifo->in + fifo->out); + /* - * Ensure that we remove the bytes from the kfifo -before- - * we update the fifo->out index. + * Ensure that we sample the fifo->out index -before- we + * start putting bytes into the kfifo. */ smp_mb(); - fifo->out += len; + off = __kfifo_off(fifo, fifo->in); + + /* first put the data starting from fifo->in to buffer end */ + l = min(len, fifo->size - off); + ret = copy_from_user(fifo->buffer + off, from, l); + + if (unlikely(ret)) + return l - ret; + + /* then put the rest (if any) at the beginning of the buffer */ + ret = copy_from_user(fifo->buffer, from + l, len - l); + + if (unlikely(ret)) + return len - ret; + + __kfifo_add_in(fifo, len); return len; } -EXPORT_SYMBOL(kfifo_out); +EXPORT_SYMBOL(kfifo_from_user); + +/** + * kfifo_to_user - gets data from the FIFO and write it to user space + * @fifo: the fifo to be used. + * @to: where the data must be copied. + * @len: the size of the destination buffer. + * + * This function copies at most @len bytes from the FIFO into the + * @to buffer and returns the number of copied bytes. + * + * Note that with only one concurrent reader and one concurrent + * writer, you don't need extra locking to use these functions. + */ +unsigned int kfifo_to_user(struct kfifo *fifo, + void __user *to, unsigned int len) +{ + unsigned int off; + unsigned int l; + int ret; + + len = min(len, fifo->in - fifo->out); + + /* + * Ensure that we sample the fifo->in index -before- we + * start removing bytes from the kfifo. + */ + + smp_rmb(); + + off = __kfifo_off(fifo, fifo->out); + + /* first get the data from fifo->out until the end of the buffer */ + l = min(len, fifo->size - off); + ret = copy_to_user(to, fifo->buffer + off, l); + + if (unlikely(ret)) + return l - ret; + + /* then get the rest (if any) from the beginning of the buffer */ + ret = copy_to_user(to + l, fifo->buffer, len - l); + + if (unlikely(ret)) + return len - ret; + + __kfifo_add_out(fifo, len); + + return len; +} +EXPORT_SYMBOL(kfifo_to_user); + -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/