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Add braces to avoid "ambiguous ‘else’" compiler warnings

Some of our "for_each_xyz()" macro constructs make gcc unhappy about
lack of braces around if-statements inside or outside the loop, because
the loop construct itself has a "if-then-else" statement inside of it.

The resulting warnings look something like this:

  drivers/gpu/drm/i915/i915_debugfs.c: In function ‘i915_dump_lrc’:
  drivers/gpu/drm/i915/i915_debugfs.c:2103:6: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses]
     if (ctx != dev_priv->kernel_context)

even if the code itself is fine.

Since the warning is fairly easy to avoid by adding a braces around the
if-statement near the for_each_xyz() construct, do so, rather than
disabling the otherwise potentially useful warning.

(The if-then-else statements used in the "for_each_xyz()" constructs are
designed to be inherently safe even with no braces, but in this case
it's quite understandable that gcc isn't really able to tell that).

This finally leaves the standard "allmodconfig" build with just a
handful of remaining warnings, so new and valid warnings hopefully will
stand out.

Signed-off-by: Linus Torvalds <>
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torvalds committed Jul 28, 2016
1 parent 124a3d8 commit 194dc870a5890e855ecffb30f3b80ba7c88f96d6
Showing with 6 additions and 3 deletions.
  1. +2 −1 drivers/gpu/drm/i915/i915_debugfs.c
  2. +2 −1 drivers/iommu/dmar.c
  3. +2 −1 drivers/iommu/intel-iommu.c
@@ -2100,9 +2100,10 @@ static int i915_dump_lrc(struct seq_file *m, void *unused)
return ret;

list_for_each_entry(ctx, &dev_priv->context_list, link)
if (ctx != dev_priv->kernel_context)
if (ctx != dev_priv->kernel_context) {
for_each_engine(engine, dev_priv)
i915_dump_lrc_obj(m, ctx, engine);


@@ -1871,10 +1871,11 @@ static int dmar_hp_remove_drhd(struct acpi_dmar_header *header, void *arg)
* All PCI devices managed by this unit should have been destroyed.
if (!dmaru->include_all && dmaru->devices && dmaru->devices_cnt)
if (!dmaru->include_all && dmaru->devices && dmaru->devices_cnt) {
dmaru->devices_cnt, i, dev)
return -EBUSY;

ret = dmar_ir_hotplug(dmaru, false);
if (ret == 0)
@@ -4272,10 +4272,11 @@ int dmar_check_one_atsr(struct acpi_dmar_header *hdr, void *arg)
if (!atsru)
return 0;

if (!atsru->include_all && atsru->devices && atsru->devices_cnt)
if (!atsru->include_all && atsru->devices && atsru->devices_cnt) {
for_each_active_dev_scope(atsru->devices, atsru->devices_cnt,
i, dev)
return -EBUSY;

return 0;

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