From f84adf4921ae3115502f44ff467b04bf2f88cf04 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Wed, 13 Feb 2013 13:01:55 -0500 Subject: xen-blkfront: drop the use of llist_for_each_entry_safe Replace llist_for_each_entry_safe with a while loop. llist_for_each_entry_safe can trigger a bug in GCC 4.1, so it's best to remove it and use a while loop and do the deletion manually. Specifically this bug can be triggered by hot-unplugging a disk, either by doing xm block-detach or by save/restore cycle. BUG: unable to handle kernel paging request at fffffffffffffff0 IP: [] blkif_free+0x63/0x130 [xen_blkfront] The crash call trace is: ... bad_area_nosemaphore+0x13/0x20 do_page_fault+0x25e/0x4b0 page_fault+0x25/0x30 ? blkif_free+0x63/0x130 [xen_blkfront] blkfront_resume+0x46/0xa0 [xen_blkfront] xenbus_dev_resume+0x6c/0x140 pm_op+0x192/0x1b0 device_resume+0x82/0x1e0 dpm_resume+0xc9/0x1a0 dpm_resume_end+0x15/0x30 do_suspend+0x117/0x1e0 When drilling down to the assembler code, on newer GCC it does .L29: cmpq $-16, %r12 #, persistent_gnt check je .L30 #, out of the loop .L25: ... code in the loop testq %r13, %r13 # n je .L29 #, back to the top of the loop cmpq $-16, %r12 #, persistent_gnt check movq 16(%r12), %r13 # .node.next, n jne .L25 #, back to the top of the loop .L30: While on GCC 4.1, it is: L78: ... code in the loop testq %r13, %r13 # n je .L78 #, back to the top of the loop movq 16(%rbx), %r13 # .node.next, n jmp .L78 #, back to the top of the loop Which basically means that the exit loop condition instead of being: &(pos)->member != NULL; is: ; which makes the loop unbound. Since xen-blkfront is the only user of the llist_for_each_entry_safe macro remove it from llist.h. Orabug: 16263164 CC: stable@vger.kernel.org Signed-off-by: Konrad Rzeszutek Wilk --- include/linux/llist.h | 25 ------------------------- 1 file changed, 25 deletions(-) (limited to 'include') diff --git a/include/linux/llist.h b/include/linux/llist.h index d0ab98f73d38..a5199f6d0e82 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h @@ -124,31 +124,6 @@ static inline void init_llist_head(struct llist_head *list) &(pos)->member != NULL; \ (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member)) -/** - * llist_for_each_entry_safe - iterate safely against remove over some entries - * of lock-less list of given type. - * @pos: the type * to use as a loop cursor. - * @n: another type * to use as a temporary storage. - * @node: the fist entry of deleted list entries. - * @member: the name of the llist_node with the struct. - * - * In general, some entries of the lock-less list can be traversed - * safely only after being removed from list, so start with an entry - * instead of list head. This variant allows removal of entries - * as we iterate. - * - * If being used on entries deleted from lock-less list directly, the - * traverse order is from the newest to the oldest added entry. If - * you want to traverse from the oldest to the newest, you must - * reverse the order by yourself before traversing. - */ -#define llist_for_each_entry_safe(pos, n, node, member) \ - for ((pos) = llist_entry((node), typeof(*(pos)), member), \ - (n) = (pos)->member.next; \ - &(pos)->member != NULL; \ - (pos) = llist_entry(n, typeof(*(pos)), member), \ - (n) = (&(pos)->member != NULL) ? (pos)->member.next : NULL) - /** * llist_empty - tests whether a lock-less list is empty * @head: the list to test -- cgit v1.2.3