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Declare FontConfig not threadsafe.

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Some time ago FontConfig stopped being thread antagonistic and
documented that it was thread safe (or at least any thread un-safety was
a bug). However, until
447b9ccc7d
at least one of the basic atomic primitives was implemented incorrectly.

Resume using a mutex to serialize access to FontConfig until 2.13.93.

Bug: cl/339089311
Change-Id: I632f03bc575a37b5391390a0868aef256e3aacda
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/331339
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
This commit is contained in:
Ben Wagner 2020-11-02 12:15:20 -05:00 committed by Skia Commit-Bot
parent 753c1b3368
commit c22288fbdb
2 changed files with 16 additions and 11 deletions
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14
src/ports/SkFontConfigInterface_direct.cpp
View File

@ -25,31 +25,33 @@
namespace {
// Fontconfig is not threadsafe before 2.10.91. Before that, we lock with a global mutex.
// See https://bug.skia.org/1497 for background.
// FontConfig was thread antagonistic until 2.10.91 with known thread safety issues until 2.13.93.
// Before that, lock with a global mutex.
// See https://bug.skia.org/1497 and cl/339089311 for background.
static SkMutex& f_c_mutex() {
static SkMutex& mutex = *(new SkMutex);
return mutex;
}
struct FCLocker {
// Assume FcGetVersion() has always been thread safe.
static constexpr int FontConfigThreadSafeVersion = 21393;
// Assume FcGetVersion() has always been thread safe.
FCLocker() {
if (FcGetVersion() < 21091) {
if (FcGetVersion() < FontConfigThreadSafeVersion) {
f_c_mutex().acquire();
}
}
~FCLocker() {
AssertHeld();
if (FcGetVersion() < 21091) {
if (FcGetVersion() < FontConfigThreadSafeVersion) {
f_c_mutex().release();
}
}
static void AssertHeld() { SkDEBUGCODE(
if (FcGetVersion() < 21091) {
if (FcGetVersion() < FontConfigThreadSafeVersion) {
f_c_mutex().assertHeld();
}
) }

13
src/ports/SkFontMgr_fontconfig.cpp
View File

@ -57,23 +57,26 @@ class SkData;
namespace {
// Fontconfig is not threadsafe before 2.10.91. Before that, we lock with a global mutex.
// See https://bug.skia.org/1497 for background.
// FontConfig was thread antagonistic until 2.10.91 with known thread safety issues until 2.13.93.
// Before that, lock with a global mutex.
// See https://bug.skia.org/1497 and cl/339089311 for background.
static SkMutex& f_c_mutex() {
static SkMutex& mutex = *(new SkMutex);
return mutex;
}
class FCLocker {
static constexpr int FontConfigThreadSafeVersion = 21393;
// Assume FcGetVersion() has always been thread safe.
static void lock() SK_NO_THREAD_SAFETY_ANALYSIS {
if (FcGetVersion() < 21091) {
if (FcGetVersion() < FontConfigThreadSafeVersion) {
f_c_mutex().acquire();
}
}
static void unlock() SK_NO_THREAD_SAFETY_ANALYSIS {
AssertHeld();
if (FcGetVersion() < 21091) {
if (FcGetVersion() < FontConfigThreadSafeVersion) {
f_c_mutex().release();
}
}
@ -93,7 +96,7 @@ public:
};
static void AssertHeld() { SkDEBUGCODE(
if (FcGetVersion() < 21091) {
if (FcGetVersion() < FontConfigThreadSafeVersion) {
f_c_mutex().assertHeld();
}
) }