The following commit has been merged into the perf/core branch of tip:
Commit-ID: 6ffe8c7d871b327d16ae6b6f1db4c8ecb0f15c64
Gitweb: https://git.kernel.org/tip/6ffe8c7d871b327d16ae6b6f1db4c8ecb0f15c64
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Sun, 29 Sep 2024 16:42:44 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 07 Oct 2024 09:28:44 +02:00
uprobes: simplify xol_take_insn_slot() and its caller
The do / while (slot_nr >= UINSNS_PER_PAGE) loop in xol_take_insn_slot()
makes no sense, the checked condition is always true. Change this code
to use the "for (;;)" loop, this way we do not need to change slot_nr if
test_and_set_bit() fails.
Also, kill the unnecessary xol_vaddr != NULL check in xol_get_insn_slot(),
xol_take_insn_slot() never returns NULL.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240929144244.GA9480@xxxxxxxxxx
---
kernel/events/uprobes.c | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 03035a8..616b5ff 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1628,25 +1628,20 @@ void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
*/
static unsigned long xol_take_insn_slot(struct xol_area *area)
{
- unsigned long slot_addr;
- int slot_nr;
+ unsigned int slot_nr;
- do {
+ for (;;) {
slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE);
if (slot_nr < UINSNS_PER_PAGE) {
if (!test_and_set_bit(slot_nr, area->bitmap))
break;
-
- slot_nr = UINSNS_PER_PAGE;
continue;
}
wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE));
- } while (slot_nr >= UINSNS_PER_PAGE);
+ }
- slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES);
atomic_inc(&area->slot_count);
-
- return slot_addr;
+ return area->vaddr + slot_nr * UPROBE_XOL_SLOT_BYTES;
}
/*
@@ -1663,12 +1658,8 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
return 0;
xol_vaddr = xol_take_insn_slot(area);
- if (unlikely(!xol_vaddr))
- return 0;
-
arch_uprobe_copy_ixol(area->page, xol_vaddr,
&uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
-
return xol_vaddr;
}
|