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SharpYuvConvert: fix a race on SharpYuvGetCPUInfo

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Rather than make a copy, requiring an additional lock/unlock only to set
the pointer to itself, pass the address of SharpYuvGetCPUInfo and use it
as a sentinel to avoid updating the pointer.

Change-Id: I22fb467f1659c16805c0d3bc7aaeba6a1bb16dbb
This commit is contained in:
James Zern 2022-10-27 13:43:32 -07:00
parent a458e3086c
commit ce2f2d668e
1 changed files with 7 additions and 2 deletions
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9
sharpyuv/sharpyuv.c
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@ -439,7 +439,11 @@ void SharpYuvInit(VP8CPUInfo cpu_info_func) {
static volatile VP8CPUInfo sharpyuv_last_cpuinfo_used = static volatile VP8CPUInfo sharpyuv_last_cpuinfo_used =
(VP8CPUInfo)&sharpyuv_last_cpuinfo_used; (VP8CPUInfo)&sharpyuv_last_cpuinfo_used;
LOCK_ACCESS; LOCK_ACCESS;
SharpYuvGetCPUInfo = cpu_info_func; // Only update SharpYuvGetCPUInfo when called from external code to avoid a
// race on reading the value in SharpYuvConvert().
if (cpu_info_func != (VP8CPUInfo)&SharpYuvGetCPUInfo) {
SharpYuvGetCPUInfo = cpu_info_func;
}
if (sharpyuv_last_cpuinfo_used == SharpYuvGetCPUInfo) { if (sharpyuv_last_cpuinfo_used == SharpYuvGetCPUInfo) {
UNLOCK_ACCESS_AND_RETURN; UNLOCK_ACCESS_AND_RETURN;
} }
@ -484,7 +488,8 @@ int SharpYuvConvert(const void* r_ptr, const void* g_ptr,
// Stride should be even for uint16_t buffers. // Stride should be even for uint16_t buffers.
return 0; return 0;
} }
SharpYuvInit(SharpYuvGetCPUInfo); // The address of the function pointer is used to avoid a read race.
SharpYuvInit((VP8CPUInfo)&SharpYuvGetCPUInfo);
// Add scaling factor to go from rgb_bit_depth to yuv_bit_depth, to the // Add scaling factor to go from rgb_bit_depth to yuv_bit_depth, to the
// rgb->yuv conversion matrix. // rgb->yuv conversion matrix.