2020-08-31 22:53:02

by Davidlohr Bueso

Subject: [PATCH] MIPS: Use rcu to lookup a task in mipsmt_sys_sched_setaffinity()

The call simply looks up the corresponding task (without iterating
the tasklist), which is safe under rcu instead of the tasklist_lock.
In addition, the setaffinity counter part already does this.

Signed-off-by: Davidlohr Bueso <[email protected]>
---
arch/mips/kernel/mips-mt-fpaff.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/mips-mt-fpaff.c b/arch/mips/kernel/mips-mt-fpaff.c
index 1a08428eedcf..6c590ef27648 100644
--- a/arch/mips/kernel/mips-mt-fpaff.c
+++ b/arch/mips/kernel/mips-mt-fpaff.c
@@ -167,7 +167,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
return -EINVAL;

get_online_cpus();
- read_lock(&tasklist_lock);
+ rcu_read_lock();

retval = -ESRCH;
p = find_process_by_pid(pid);
@@ -181,7 +181,7 @@ asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
cpumask_and(&mask, &allowed, cpu_active_mask);

out_unlock:
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
put_online_cpus();
if (retval)
return retval;
--
2.26.2

2020-09-03 08:30:43

by Thomas Bogendoerfer

Subject: Re: [PATCH] MIPS: Use rcu to lookup a task in mipsmt_sys_sched_setaffinity()

On Mon, Aug 31, 2020 at 01:14:02PM -0700, Davidlohr Bueso wrote:
> The call simply looks up the corresponding task (without iterating
> the tasklist), which is safe under rcu instead of the tasklist_lock.
> In addition, the setaffinity counter part already does this.
>
> Signed-off-by: Davidlohr Bueso <[email protected]>
> ---
> arch/mips/kernel/mips-mt-fpaff.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)

applied to mips-next.

Thomas.

--
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good idea. [ RFC1925, 2.3 ]