| Message ID | 20200206035654.2647-1-cai@lca.pw (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [-next] mm/page_io: mark an intentional data race | expand |
Please disregard this patch. I found more data races in this file, so will send a new patch to have them at once. > On Feb 5, 2020, at 10:56 PM, Qian Cai <cai@lca.pw> wrote: > > struct swap_info_struct si.flags could be accessed concurrently as > noticed by KCSAN, > > BUG: KCSAN: data-race in scan_swap_map_slots / swap_readpage > > write to 0xffff9c77b80ac400 of 8 bytes by task 91325 on cpu 16: > scan_swap_map_slots+0x6fe/0xb50 > scan_swap_map_slots at mm/swapfile.c:887 > get_swap_pages+0x39d/0x5c0 > get_swap_page+0x377/0x524 > add_to_swap+0xe4/0x1c0 > shrink_page_list+0x1740/0x2820 > shrink_inactive_list+0x316/0x8b0 > shrink_lruvec+0x8dc/0x1380 > shrink_node+0x317/0xd80 > do_try_to_free_pages+0x1f7/0xa10 > try_to_free_pages+0x26c/0x5e0 > __alloc_pages_slowpath+0x458/0x1290 > __alloc_pages_nodemask+0x3bb/0x450 > alloc_pages_vma+0x8a/0x2c0 > do_anonymous_page+0x170/0x700 > __handle_mm_fault+0xc9f/0xd00 > handle_mm_fault+0xfc/0x2f0 > do_page_fault+0x263/0x6f9 > page_fault+0x34/0x40 > > read to 0xffff9c77b80ac400 of 8 bytes by task 5422 on cpu 7: > swap_readpage+0x204/0x6a0 > swap_readpage at mm/page_io.c:380 > read_swap_cache_async+0xa2/0xb0 > swapin_readahead+0x6a0/0x890 > do_swap_page+0x465/0xeb0 > __handle_mm_fault+0xc7a/0xd00 > handle_mm_fault+0xfc/0x2f0 > do_page_fault+0x263/0x6f9 > page_fault+0x34/0x40 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 7 PID: 5422 Comm: gmain Tainted: G W O L 5.5.0-next-20200204+ #6 > Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 > > The write is under &si->lock, but the read is done as lockless. Since > the read only check for a specific bit in the flag, it is harmless even > if load tearing happens. Thus, just mark it as an intentional data race > using the data_race() macro. > > Signed-off-by: Qian Cai <cai@lca.pw> > --- > mm/page_io.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_io.c b/mm/page_io.c > index 76965be1d40e..e33925b9178c 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -377,7 +377,7 @@ int swap_readpage(struct page *page, bool synchronous) > goto out; > } > > - if (sis->flags & SWP_FS) { > + if (data_race(sis->flags & SWP_FS)) { > struct file *swap_file = sis->swap_file; > struct address_space *mapping = swap_file->f_mapping; > > -- > 2.21.0 (Apple Git-122.2) >
diff --git a/mm/page_io.c b/mm/page_io.c index 76965be1d40e..e33925b9178c 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -377,7 +377,7 @@ int swap_readpage(struct page *page, bool synchronous) goto out; } - if (sis->flags & SWP_FS) { + if (data_race(sis->flags & SWP_FS)) { struct file *swap_file = sis->swap_file; struct address_space *mapping = swap_file->f_mapping;
struct swap_info_struct si.flags could be accessed concurrently as noticed by KCSAN, BUG: KCSAN: data-race in scan_swap_map_slots / swap_readpage write to 0xffff9c77b80ac400 of 8 bytes by task 91325 on cpu 16: scan_swap_map_slots+0x6fe/0xb50 scan_swap_map_slots at mm/swapfile.c:887 get_swap_pages+0x39d/0x5c0 get_swap_page+0x377/0x524 add_to_swap+0xe4/0x1c0 shrink_page_list+0x1740/0x2820 shrink_inactive_list+0x316/0x8b0 shrink_lruvec+0x8dc/0x1380 shrink_node+0x317/0xd80 do_try_to_free_pages+0x1f7/0xa10 try_to_free_pages+0x26c/0x5e0 __alloc_pages_slowpath+0x458/0x1290 __alloc_pages_nodemask+0x3bb/0x450 alloc_pages_vma+0x8a/0x2c0 do_anonymous_page+0x170/0x700 __handle_mm_fault+0xc9f/0xd00 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 read to 0xffff9c77b80ac400 of 8 bytes by task 5422 on cpu 7: swap_readpage+0x204/0x6a0 swap_readpage at mm/page_io.c:380 read_swap_cache_async+0xa2/0xb0 swapin_readahead+0x6a0/0x890 do_swap_page+0x465/0xeb0 __handle_mm_fault+0xc7a/0xd00 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 Reported by Kernel Concurrency Sanitizer on: CPU: 7 PID: 5422 Comm: gmain Tainted: G W O L 5.5.0-next-20200204+ #6 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 The write is under &si->lock, but the read is done as lockless. Since the read only check for a specific bit in the flag, it is harmless even if load tearing happens. Thus, just mark it as an intentional data race using the data_race() macro. Signed-off-by: Qian Cai <cai@lca.pw> --- mm/page_io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)