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rseq: Extend struct rseq with numa node id

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Adding the NUMA node id to struct rseq is a straightforward thing to do,
and a good way to figure out if anything in the user-space ecosystem
prevents extending struct rseq.

This NUMA node id field allows memory allocators such as tcmalloc to
take advantage of fast access to the current NUMA node id to perform
NUMA-aware memory allocation.

It can also be useful for implementing fast-paths for NUMA-aware
user-space mutexes.

It also allows implementing getcpu(2) purely in user-space.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221122203932.231377-5-mathieu.desnoyers@efficios.com
This commit is contained in:
Mathieu Desnoyers
2022-11-22 15:39:06 -05:00
committed by Peter Zijlstra
parent ee3e3ac05c
commit cbae6bac29
3 changed files with 24 additions and 7 deletions
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19
kernel/rseq.c
View File

@@ -85,15 +85,17 @@
* F1. <failure>
*/
static int rseq_update_cpu_id(struct task_struct *t)
static int rseq_update_cpu_node_id(struct task_struct *t)
{
u32 cpu_id = raw_smp_processor_id();
struct rseq __user *rseq = t->rseq;
u32 cpu_id = raw_smp_processor_id();
u32 node_id = cpu_to_node(cpu_id);
if (!user_write_access_begin(rseq, t->rseq_len))
goto efault;
unsafe_put_user(cpu_id, &rseq->cpu_id_start, efault_end);
unsafe_put_user(cpu_id, &rseq->cpu_id, efault_end);
unsafe_put_user(node_id, &rseq->node_id, efault_end);
/*
* Additional feature fields added after ORIG_RSEQ_SIZE
* need to be conditionally updated only if
@@ -109,9 +111,9 @@ efault:
return -EFAULT;
}
static int rseq_reset_rseq_cpu_id(struct task_struct *t)
static int rseq_reset_rseq_cpu_node_id(struct task_struct *t)
{
u32 cpu_id_start = 0, cpu_id = RSEQ_CPU_ID_UNINITIALIZED;
u32 cpu_id_start = 0, cpu_id = RSEQ_CPU_ID_UNINITIALIZED, node_id = 0;
/*
* Reset cpu_id_start to its initial state (0).
@@ -125,6 +127,11 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t)
*/
if (put_user(cpu_id, &t->rseq->cpu_id))
return -EFAULT;
/*
* Reset node_id to its initial state (0).
*/
if (put_user(node_id, &t->rseq->node_id))
return -EFAULT;
/*
* Additional feature fields added after ORIG_RSEQ_SIZE
* need to be conditionally reset only if
@@ -314,7 +321,7 @@ void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs)
if (unlikely(ret < 0))
goto error;
}
if (unlikely(rseq_update_cpu_id(t)))
if (unlikely(rseq_update_cpu_node_id(t)))
goto error;
return;
@@ -361,7 +368,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
return -EINVAL;
if (current->rseq_sig != sig)
return -EPERM;
ret = rseq_reset_rseq_cpu_id(current);
ret = rseq_reset_rseq_cpu_node_id(current);
if (ret)
return ret;
current->rseq = NULL;