The patch titled
Subject: mm/vmalloc: use raw_cpu_ptr() for vmap_block_queue access.
has been added to the -mm mm-unstable branch. Its filename is
mm-vmalloc-use-raw_cpu_ptr-for-vmap_block_queue-access.patch
This patch should soon appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: mm/vmalloc: use raw_cpu_ptr() for vmap_block_queue access.
The per-CPU resource vmap_block_queue is accessed via the get_cpu_var().
That macro disables preemption and then loads the pointer from the current
CPU.
This doesn't work on PREEMPT_RT because a spinlock_t is later accessed
within the preempt-disable section.
There is no need to disable preemption while accessing the per-CPU struct
vmap_block_queue because the list is protected with a spinlock_t. The
per-CPU struct is also accessed cross-CPU in purge_fragmented_blocks().
It is possible that by using raw_cpu_ptr() the code migrates to another
CPU and uses struct from another CPU. This is fine because the list is
locked and the locked section is very short.
Use raw_cpu_ptr() to access vmap_block_queue.
Link: https://lkml.kernel.org/r/YnKx3duAB53P7ojN@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmalloc.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- a/mm/vmalloc.c~mm-vmalloc-use-raw_cpu_ptr-for-vmap_block_queue-access
+++ a/mm/vmalloc.c
@@ -1938,11 +1938,10 @@ static void *new_vmap_block(unsigned int
return ERR_PTR(err);
}
- vbq = &get_cpu_var(vmap_block_queue);
+ vbq = raw_cpu_ptr(&vmap_block_queue);
spin_lock(&vbq->lock);
list_add_tail_rcu(&vb->free_list, &vbq->free);
spin_unlock(&vbq->lock);
- put_cpu_var(vmap_block_queue);
return vaddr;
}
@@ -2021,7 +2020,7 @@ static void *vb_alloc(unsigned long size
order = get_order(size);
rcu_read_lock();
- vbq = &get_cpu_var(vmap_block_queue);
+ vbq = raw_cpu_ptr(&vmap_block_queue);
list_for_each_entry_rcu(vb, &vbq->free, free_list) {
unsigned long pages_off;
@@ -2044,7 +2043,6 @@ static void *vb_alloc(unsigned long size
break;
}
- put_cpu_var(vmap_block_queue);
rcu_read_unlock();
/* Allocate new block if nothing was found */
_
Patches currently in -mm which might be from bigeasy@xxxxxxxxxxxxx are
mm-vmalloc-use-raw_cpu_ptr-for-vmap_block_queue-access.patch
