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LibC: Cleanup TSC clock_gettime control flow

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Bananymous
2026-08-24 01:37:05 +03:00
parent cd6269d406
commit 2e22ebf0b5
1 changed files with 12 additions and 17 deletions
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userspace/libraries/LibC/time.cpp
+6 -11
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@@ -47,30 +47,25 @@ int clock_gettime(clockid_t clock_id, struct timespec* tp)
} while (seq1 != seq2 || (seq1 & 1)); } while (seq1 != seq2 || (seq1 & 1));
}; };
read_tsc_info:
if (g_shared_page->features & Kernel::API::SPF_RDTSCP) if (g_shared_page->features & Kernel::API::SPF_RDTSCP)
{ {
do {
uint32_t cpu; uint32_t cpu;
curr_tsc = __builtin_ia32_rdtscp(&cpu); curr_tsc = __builtin_ia32_rdtscp(&cpu);
read_tsc_info(g_shared_page->cpus[cpu].gettime_local); read_tsc_info(g_shared_page->cpus[cpu].gettime_local);
} while (curr_tsc < last_tsc);
} }
else for (;;) else
{ {
uint16_t cpu1, cpu2; uint16_t cpu1, cpu2;
do {
asm volatile("lsl %1, %0" : "=r"(cpu1) : "r"(g_shared_page->gdt_cpu_offset)); asm volatile("lsl %1, %0" : "=r"(cpu1) : "r"(g_shared_page->gdt_cpu_offset));
read_tsc_info(g_shared_page->cpus[cpu1].gettime_local);
curr_tsc = __builtin_ia32_rdtsc(); curr_tsc = __builtin_ia32_rdtsc();
asm volatile("lsl %1, %0" : "=r"(cpu2) : "r"(g_shared_page->gdt_cpu_offset)); asm volatile("lsl %1, %0" : "=r"(cpu2) : "r"(g_shared_page->gdt_cpu_offset));
if (cpu1 != cpu2) } while (cpu1 != cpu2);
continue;
read_tsc_info(g_shared_page->cpus[cpu1].gettime_local);
break;
} }
// NOTE: as we read TSC before getting the calibration, it is possible
// for the calibration to get updated in between.
if (curr_tsc < last_tsc)
goto read_tsc_info;
uint64_t clock_ns = curr_tsc - last_tsc; uint64_t clock_ns = curr_tsc - last_tsc;
if (shift >= 0) if (shift >= 0)
clock_ns <<= shift; clock_ns <<= shift;