linux-kernel - [PATCH 3.2 010/107] MIPS: Fix sched_getaffinity with MT FPAFF enabled

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Message-ID: <lsq.1444349547.644827378@decadent.org.uk>
Date:	Fri, 09 Oct 2015 01:12:27 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Ralf Baechle" <ralf@...ux-mips.org>,
	"Felix Fietkau" <nbd@...nwrt.org>, linux-mips@...ux-mips.org
Subject: [PATCH 3.2 010/107] MIPS: Fix sched_getaffinity with MT FPAFF enabled

3.2.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Felix Fietkau <nbd@...nwrt.org>

commit 1d62d737555e1378eb62a8bba26644f7d97139d2 upstream.

p->thread.user_cpus_allowed is zero-initialized and is only filled on
the first sched_setaffinity call.

To avoid adding overhead in the task initialization codepath, simply OR
the returned mask in sched_getaffinity with p->cpus_allowed.

Signed-off-by: Felix Fietkau <nbd@...nwrt.org>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10740/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
[bwh: Backported to 3.2: also convert from obsolete cpumask API]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/mips/kernel/mips-mt-fpaff.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/arch/mips/kernel/mips-mt-fpaff.c
+++ b/arch/mips/kernel/mips-mt-fpaff.c
@@ -154,7 +154,7 @@ asmlinkage long mipsmt_sys_sched_getaffi
 				      unsigned long __user *user_mask_ptr)
 {
 	unsigned int real_len;
-	cpumask_t mask;
+	cpumask_t allowed, mask;
 	int retval;
 	struct task_struct *p;
 
@@ -173,7 +173,8 @@ asmlinkage long mipsmt_sys_sched_getaffi
 	if (retval)
 		goto out_unlock;
 
-	cpus_and(mask, p->thread.user_cpus_allowed, cpu_possible_map);
+	cpumask_or(&allowed, &p->thread.user_cpus_allowed, &p->cpus_allowed);
+	cpumask_and(&mask, &allowed, cpu_active_mask);
 
 out_unlock:
 	read_unlock(&tasklist_lock);

--
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