From mboxrd@z Thu Jan 1 00:00:00 1970 From: adrienverge@gmail.com (=?UTF-8?q?Adrien=20Verg=C3=A9?=) Date: Fri, 24 Jan 2014 11:40:56 -0500 Subject: [PATCH V2 6/6] ARM CoreSight: ETM: Allocate a trace buffer only when necessary In-Reply-To: <1390581656-16372-1-git-send-email-adrienverge@gmail.com> References: <1390581656-16372-1-git-send-email-adrienverge@gmail.com> Message-ID: <1390581656-16372-7-git-send-email-adrienverge@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Some user applications try to retrieve trace data often, there is no need to call vmalloc() when there is 0 byte to fetch. Signed-off-by: Adrien Verg? --- arch/arm/kernel/etm.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm/kernel/etm.c b/arch/arm/kernel/etm.c index 54b5128..bc97240 100644 --- a/arch/arm/kernel/etm.c +++ b/arch/arm/kernel/etm.c @@ -309,7 +309,7 @@ static ssize_t etb_read(struct file *file, char __user *data, long length; struct tracectx *t = file->private_data; u32 first = 0; - u32 *buf; + u32 *buf = NULL; mutex_lock(&t->mutex); @@ -327,12 +327,14 @@ static ssize_t etb_read(struct file *file, char __user *data, etb_writel(t, first, ETBR_READADDR); length = min(total * 4, (int)len); - buf = vmalloc(length); + if (length != 0) + buf = vmalloc(length); dev_dbg(t->dev, "ETB buffer length: %d\n", total); dev_dbg(t->dev, "ETB status reg: %x\n", etb_readl(t, ETBR_STATUS)); - for (i = 0; i < length / 4; i++) - buf[i] = etb_readl(t, ETBR_READMEM); + if (buf) + for (i = 0; i < length / 4; i++) + buf[i] = etb_readl(t, ETBR_READMEM); /* the only way to deassert overflow bit in ETB status is this */ etb_writel(t, 1, ETBR_CTRL); @@ -345,7 +347,8 @@ static ssize_t etb_read(struct file *file, char __user *data, etb_lock(t); length -= copy_to_user(data, buf, length); - vfree(buf); + if (buf) + vfree(buf); out: mutex_unlock(&t->mutex); -- 1.8.5.2