lkml.org 
[lkml]   [2017]   [Apr]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/4] mm/vmalloc: allow to call vfree() in atomic context
    On Thu 30-03-17 13:27:16, Andrey Ryabinin wrote:
    > Commit 5803ed292e63 ("mm: mark all calls into the vmalloc subsystem
    > as potentially sleeping") added might_sleep() to remove_vm_area() from
    > vfree(), and commit 763b218ddfaf ("mm: add preempt points into
    > __purge_vmap_area_lazy()") actually made vfree() potentially sleeping.
    >
    > This broke vmwgfx driver which calls vfree() under spin_lock().
    >
    > BUG: sleeping function called from invalid context at mm/vmalloc.c:1480
    > in_atomic(): 1, irqs_disabled(): 0, pid: 341, name: plymouthd
    > 2 locks held by plymouthd/341:
    > #0: (drm_global_mutex){+.+.+.}, at: [<ffffffffc01c274b>] drm_release+0x3b/0x3b0 [drm]
    > #1: (&(&tfile->lock)->rlock){+.+...}, at: [<ffffffffc0173038>] ttm_object_file_release+0x28/0x90 [ttm]
    >
    > Call Trace:
    > dump_stack+0x86/0xc3
    > ___might_sleep+0x17d/0x250
    > __might_sleep+0x4a/0x80
    > remove_vm_area+0x22/0x90
    > __vunmap+0x2e/0x110
    > vfree+0x42/0x90
    > kvfree+0x2c/0x40
    > drm_ht_remove+0x1a/0x30 [drm]
    > ttm_object_file_release+0x50/0x90 [ttm]
    > vmw_postclose+0x47/0x60 [vmwgfx]
    > drm_release+0x290/0x3b0 [drm]
    > __fput+0xf8/0x210
    > ____fput+0xe/0x10
    > task_work_run+0x85/0xc0
    > exit_to_usermode_loop+0xb4/0xc0
    > do_syscall_64+0x185/0x1f0
    > entry_SYSCALL64_slow_path+0x25/0x25
    >
    > This can be fixed in vmgfx, but it would be better to make vfree()
    > non-sleeping again because we may have other bugs like this one.
    >
    > __purge_vmap_area_lazy() is the only function in the vfree() path that
    > wants to be able to sleep. So it make sense to schedule
    > __purge_vmap_area_lazy() via schedule_work() so it runs only in sleepable
    > context. This will have a minimal effect on the regular vfree() path.
    > since __purge_vmap_area_lazy() is rarely called.
    >
    > Fixes: 5803ed292e63 ("mm: mark all calls into the vmalloc subsystem as
    > potentially sleeping")
    > Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
    > Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
    > Cc: <stable@vger.kernel.org>

    Yes I believe this is an enhancements.
    Acked-by: Michal Hocko <mhocko@suse.com>

    Crawling over all vfree users is just unfeasible.

    > Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
    > ---
    > mm/vmalloc.c | 9 ++++-----
    > 1 file changed, 4 insertions(+), 5 deletions(-)
    >
    > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
    > index 68eb002..ea1b4ab 100644
    > --- a/mm/vmalloc.c
    > +++ b/mm/vmalloc.c
    > @@ -701,7 +701,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
    > * Kick off a purge of the outstanding lazy areas. Don't bother if somebody
    > * is already purging.
    > */
    > -static void try_purge_vmap_area_lazy(void)
    > +static void try_purge_vmap_area_lazy(struct work_struct *work)
    > {
    > if (mutex_trylock(&vmap_purge_lock)) {
    > __purge_vmap_area_lazy(ULONG_MAX, 0);
    > @@ -720,6 +720,8 @@ static void purge_vmap_area_lazy(void)
    > mutex_unlock(&vmap_purge_lock);
    > }
    >
    > +static DECLARE_WORK(purge_vmap_work, try_purge_vmap_area_lazy);
    > +
    > /*
    > * Free a vmap area, caller ensuring that the area has been unmapped
    > * and flush_cache_vunmap had been called for the correct range
    > @@ -736,7 +738,7 @@ static void free_vmap_area_noflush(struct vmap_area *va)
    > llist_add(&va->purge_list, &vmap_purge_list);
    >
    > if (unlikely(nr_lazy > lazy_max_pages()))
    > - try_purge_vmap_area_lazy();
    > + schedule_work(&purge_vmap_work);
    > }
    >
    > /*
    > @@ -1125,7 +1127,6 @@ void vm_unmap_ram(const void *mem, unsigned int count)
    > unsigned long addr = (unsigned long)mem;
    > struct vmap_area *va;
    >
    > - might_sleep();
    > BUG_ON(!addr);
    > BUG_ON(addr < VMALLOC_START);
    > BUG_ON(addr > VMALLOC_END);
    > @@ -1477,8 +1478,6 @@ struct vm_struct *remove_vm_area(const void *addr)
    > {
    > struct vmap_area *va;
    >
    > - might_sleep();
    > -
    > va = find_vmap_area((unsigned long)addr);
    > if (va && va->flags & VM_VM_AREA) {
    > struct vm_struct *vm = va->vm;
    > --
    > 2.10.2
    >
    > --
    > To unsubscribe, send a message with 'unsubscribe linux-mm' in
    > the body to majordomo@kvack.org. For more info on Linux MM,
    > see: http://www.linux-mm.org/ .
    > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

    --
    Michal Hocko
    SUSE Labs

    \
     
     \ /
      Last update: 2017-04-04 11:39    [W:8.983 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site