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de800d8305
Remove the __slowexp code, so exp is no longer correctly rounded. The result is computed to about 70 bits precision so the worst case ulp error is about 0.500007 in nearest rounding mode. * manual/probes.texi: Remove slowexp probes. * math/Makefile: Remove slowexp. * sysdeps/generic/math_private.h (__slowexp): Remove. * sysdeps/ieee754/dbl-64/e_exp.c (__ieee754_exp): Remove __slowexp and document error bounds. * sysdeps/i386/fpu/slowexp.c: Remove. * sysdeps/ia64/fpu/slowexp.c: Remove. * sysdeps/ieee754/dbl-64/slowexp.c: Remove. * sysdeps/ieee754/dbl-64/uexp.h (err_0): Remove. * sysdeps/m68k/m680x0/fpu/slowexp.c: Remove. * sysdeps/powerpc/power4/fpu/Makefile (CPPFLAGS-slowexp.c): Remove. * sysdeps/x86_64/fpu/multiarch/Makefile: Remove slowexp-fma. * sysdeps/x86_64/fpu/multiarch/e_exp-avx.c (__slowexp): Remove. * sysdeps/x86_64/fpu/multiarch/e_exp-fma.c (__slowexp): Remove. * sysdeps/x86_64/fpu/multiarch/e_exp-fma4.c (__slowexp): Remove. * sysdeps/x86_64/fpu/multiarch/slowexp-avx.c: Remove. * sysdeps/x86_64/fpu/multiarch/slowexp-fma.c: Remove. * sysdeps/x86_64/fpu/multiarch/slowexp-fma4.c: Remove.
382 lines
18 KiB
Plaintext
382 lines
18 KiB
Plaintext
@node Internal Probes
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@c @node Internal Probes, Tunables, POSIX Threads, Top
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@c %MENU% Probes to monitor libc internal behavior
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@chapter Internal probes
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In order to aid in debugging and monitoring internal behavior,
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@theglibc{} exposes nearly-zero-overhead SystemTap probes marked with
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the @code{libc} provider.
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These probes are not part of the @glibcadj{} stable ABI, and they are
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subject to change or removal across releases. Our only promise with
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regard to them is that, if we find a need to remove or modify the
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arguments of a probe, the modified probe will have a different name, so
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that program monitors relying on the old probe will not get unexpected
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arguments.
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@menu
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* Memory Allocation Probes:: Probes in the memory allocation subsystem
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* Mathematical Function Probes:: Probes in mathematical functions
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* Non-local Goto Probes:: Probes in setjmp and longjmp
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@end menu
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@node Memory Allocation Probes
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@section Memory Allocation Probes
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These probes are designed to signal relatively unusual situations within
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the virtual memory subsystem of @theglibc{}.
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@deftp Probe memory_sbrk_more (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered after the main arena is extended by calling
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@code{sbrk}. Argument @var{$arg1} is the additional size requested to
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@code{sbrk}, and @var{$arg2} is the pointer that marks the end of the
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@code{sbrk} area, returned in response to the request.
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@end deftp
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@deftp Probe memory_sbrk_less (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered after the size of the main arena is decreased by
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calling @code{sbrk}. Argument @var{$arg1} is the size released by
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@code{sbrk} (the positive value, rather than the negative value passed
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to @code{sbrk}), and @var{$arg2} is the pointer that marks the end of
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the @code{sbrk} area, returned in response to the request.
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@end deftp
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@deftp Probe memory_heap_new (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered after a new heap is @code{mmap}ed. Argument
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@var{$arg1} is a pointer to the base of the memory area, where the
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@code{heap_info} data structure is held, and @var{$arg2} is the size of
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the heap.
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@end deftp
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@deftp Probe memory_heap_free (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered @emph{before} (unlike the other sbrk and heap
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probes) a heap is completely removed via @code{munmap}. Argument
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@var{$arg1} is a pointer to the heap, and @var{$arg2} is the size of the
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heap.
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@end deftp
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@deftp Probe memory_heap_more (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered after a trailing portion of an @code{mmap}ed
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heap is extended. Argument @var{$arg1} is a pointer to the heap, and
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@var{$arg2} is the new size of the heap.
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@end deftp
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@deftp Probe memory_heap_less (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered after a trailing portion of an @code{mmap}ed
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heap is released. Argument @var{$arg1} is a pointer to the heap, and
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@var{$arg2} is the new size of the heap.
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@end deftp
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@deftp Probe memory_malloc_retry (size_t @var{$arg1})
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@deftpx Probe memory_realloc_retry (size_t @var{$arg1}, void *@var{$arg2})
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@deftpx Probe memory_memalign_retry (size_t @var{$arg1}, size_t @var{$arg2})
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@deftpx Probe memory_calloc_retry (size_t @var{$arg1})
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These probes are triggered when the corresponding functions fail to
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obtain the requested amount of memory from the arena in use, before they
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call @code{arena_get_retry} to select an alternate arena in which to
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retry the allocation. Argument @var{$arg1} is the amount of memory
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requested by the user; in the @code{calloc} case, that is the total size
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computed from both function arguments. In the @code{realloc} case,
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@var{$arg2} is the pointer to the memory area being resized. In the
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@code{memalign} case, @var{$arg2} is the alignment to be used for the
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request, which may be stricter than the value passed to the
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@code{memalign} function. A @code{memalign} probe is also used by functions
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@code{posix_memalign, valloc} and @code{pvalloc}.
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Note that the argument order does @emph{not} match that of the
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corresponding two-argument functions, so that in all of these probes the
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user-requested allocation size is in @var{$arg1}.
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@end deftp
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@deftp Probe memory_arena_retry (size_t @var{$arg1}, void *@var{$arg2})
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This probe is triggered within @code{arena_get_retry} (the function
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called to select the alternate arena in which to retry an allocation
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that failed on the first attempt), before the selection of an alternate
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arena. This probe is redundant, but much easier to use when it's not
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important to determine which of the various memory allocation functions
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is failing to allocate on the first try. Argument @var{$arg1} is the
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same as in the function-specific probes, except for extra room for
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padding introduced by functions that have to ensure stricter alignment.
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Argument @var{$arg2} is the arena in which allocation failed.
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@end deftp
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@deftp Probe memory_arena_new (void *@var{$arg1}, size_t @var{$arg2})
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This probe is triggered when @code{malloc} allocates and initializes an
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additional arena (not the main arena), but before the arena is assigned
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to the running thread or inserted into the internal linked list of
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arenas. The arena's @code{malloc_state} internal data structure is
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located at @var{$arg1}, within a newly-allocated heap big enough to hold
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at least @var{$arg2} bytes.
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@end deftp
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@deftp Probe memory_arena_reuse (void *@var{$arg1}, void *@var{$arg2})
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This probe is triggered when @code{malloc} has just selected an existing
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arena to reuse, and (temporarily) reserved it for exclusive use.
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Argument @var{$arg1} is a pointer to the newly-selected arena, and
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@var{$arg2} is a pointer to the arena previously used by that thread.
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This occurs within
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@code{reused_arena}, right after the mutex mentioned in probe
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@code{memory_arena_reuse_wait} is acquired; argument @var{$arg1} will
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point to the same arena. In this configuration, this will usually only
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occur once per thread. The exception is when a thread first selected
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the main arena, but a subsequent allocation from it fails: then, and
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only then, may we switch to another arena to retry that allocation, and
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for further allocations within that thread.
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@end deftp
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@deftp Probe memory_arena_reuse_wait (void *@var{$arg1}, void *@var{$arg2}, void *@var{$arg3})
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This probe is triggered when @code{malloc} is about to wait for an arena
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to become available for reuse. Argument @var{$arg1} holds a pointer to
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the mutex the thread is going to wait on, @var{$arg2} is a pointer to a
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newly-chosen arena to be reused, and @var{$arg3} is a pointer to the
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arena previously used by that thread.
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This occurs within
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@code{reused_arena}, when a thread first tries to allocate memory or
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needs a retry after a failure to allocate from the main arena, there
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isn't any free arena, the maximum number of arenas has been reached, and
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an existing arena was chosen for reuse, but its mutex could not be
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immediately acquired. The mutex in @var{$arg1} is the mutex of the
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selected arena.
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@end deftp
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@deftp Probe memory_arena_reuse_free_list (void *@var{$arg1})
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This probe is triggered when @code{malloc} has chosen an arena that is
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in the free list for use by a thread, within the @code{get_free_list}
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function. The argument @var{$arg1} holds a pointer to the selected arena.
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@end deftp
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@deftp Probe memory_mallopt (int @var{$arg1}, int @var{$arg2})
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This probe is triggered when function @code{mallopt} is called to change
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@code{malloc} internal configuration parameters, before any change to
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the parameters is made. The arguments @var{$arg1} and @var{$arg2} are
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the ones passed to the @code{mallopt} function.
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@end deftp
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@deftp Probe memory_mallopt_mxfast (int @var{$arg1}, int @var{$arg2})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_MXFAST}, and the requested
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value is in an acceptable range. Argument @var{$arg1} is the requested
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value, and @var{$arg2} is the previous value of this @code{malloc}
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parameter.
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@end deftp
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@deftp Probe memory_mallopt_trim_threshold (int @var{$arg1}, int @var{$arg2}, int @var{$arg3})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_TRIM_THRESHOLD}. Argument
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@var{$arg1} is the requested value, @var{$arg2} is the previous value of
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this @code{malloc} parameter, and @var{$arg3} is nonzero if dynamic
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threshold adjustment was already disabled.
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@end deftp
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@deftp Probe memory_mallopt_top_pad (int @var{$arg1}, int @var{$arg2}, int @var{$arg3})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_TOP_PAD}. Argument
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@var{$arg1} is the requested value, @var{$arg2} is the previous value of
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this @code{malloc} parameter, and @var{$arg3} is nonzero if dynamic
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threshold adjustment was already disabled.
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@end deftp
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@deftp Probe memory_mallopt_mmap_threshold (int @var{$arg1}, int @var{$arg2}, int @var{$arg3})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_MMAP_THRESHOLD}, and the
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requested value is in an acceptable range. Argument @var{$arg1} is the
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requested value, @var{$arg2} is the previous value of this @code{malloc}
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parameter, and @var{$arg3} is nonzero if dynamic threshold adjustment
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was already disabled.
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@end deftp
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@deftp Probe memory_mallopt_mmap_max (int @var{$arg1}, int @var{$arg2}, int @var{$arg3})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_MMAP_MAX}. Argument
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@var{$arg1} is the requested value, @var{$arg2} is the previous value of
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this @code{malloc} parameter, and @var{$arg3} is nonzero if dynamic
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threshold adjustment was already disabled.
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@end deftp
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@deftp Probe memory_mallopt_perturb (int @var{$arg1}, int @var{$arg2})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_PERTURB}. Argument
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@var{$arg1} is the requested value, and @var{$arg2} is the previous
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value of this @code{malloc} parameter.
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@end deftp
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@deftp Probe memory_mallopt_arena_test (int @var{$arg1}, int @var{$arg2})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_ARENA_TEST}, and the
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requested value is in an acceptable range. Argument @var{$arg1} is the
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requested value, and @var{$arg2} is the previous value of this
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@code{malloc} parameter.
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@end deftp
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@deftp Probe memory_mallopt_arena_max (int @var{$arg1}, int @var{$arg2})
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This probe is triggered shortly after the @code{memory_mallopt} probe,
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when the parameter to be changed is @code{M_ARENA_MAX}, and the
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requested value is in an acceptable range. Argument @var{$arg1} is the
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requested value, and @var{$arg2} is the previous value of this
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@code{malloc} parameter.
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@end deftp
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@deftp Probe memory_mallopt_free_dyn_thresholds (int @var{$arg1}, int @var{$arg2})
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This probe is triggered when function @code{free} decides to adjust the
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dynamic brk/mmap thresholds. Argument @var{$arg1} and @var{$arg2} are
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the adjusted mmap and trim thresholds, respectively.
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@end deftp
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@deftp Probe memory_tunable_tcache_max_bytes (int @var{$arg1}, int @var{$arg2})
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This probe is triggered when the @code{glibc.malloc.tcache_max}
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tunable is set. Argument @var{$arg1} is the requested value, and
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@var{$arg2} is the previous value of this tunable.
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@end deftp
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@deftp Probe memory_tunable_tcache_count (int @var{$arg1}, int @var{$arg2})
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This probe is triggered when the @code{glibc.malloc.tcache_count}
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tunable is set. Argument @var{$arg1} is the requested value, and
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@var{$arg2} is the previous value of this tunable.
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@end deftp
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@deftp Probe memory_tunable_tcache_unsorted_limit (int @var{$arg1}, int @var{$arg2})
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This probe is triggered when the
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@code{glibc.malloc.tcache_unsorted_limit} tunable is set. Argument
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@var{$arg1} is the requested value, and @var{$arg2} is the previous
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value of this tunable.
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@end deftp
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@node Mathematical Function Probes
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@section Mathematical Function Probes
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Some mathematical functions fall back to multiple precision arithmetic for
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some inputs to get last bit precision for their return values. This multiple
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precision fallback is much slower than the default algorithms and may have a
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significant impact on application performance. The systemtap probe markers
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described in this section may help you determine if your application calls
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mathematical functions with inputs that may result in multiple-precision
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arithmetic.
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Unless explicitly mentioned otherwise, a precision of 1 implies 24 bits of
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precision in the mantissa of the multiple precision number. Hence, a precision
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level of 32 implies 768 bits of precision in the mantissa.
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@deftp Probe slowatan2 (int @var{$arg1}, double @var{$arg2}, double @var{$arg3}, double @var{$arg4})
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This probe is triggered when the @code{atan2} function is called with
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an input that results in multiple precision computation. Argument
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@var{$arg1} is the precision with which computation succeeded.
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Arguments @var{$arg2} and @var{$arg3} are inputs to the @code{atan2}
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function and @var{$arg4} is the computed result.
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@end deftp
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@deftp Probe slowatan2_inexact (int @var{$arg1}, double @var{$arg2}, double @var{$arg3}, double @var{$arg4})
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This probe is triggered when the @code{atan} function is called with
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an input that results in multiple precision computation and none of
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the multiple precision computations result in an accurate result.
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Argument @var{$arg1} is the maximum precision with which computations
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were performed. Arguments @var{$arg2} and @var{$arg3} are inputs to
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the @code{atan2} function and @var{$arg4} is the computed result.
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@end deftp
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@deftp Probe slowatan (int @var{$arg1}, double @var{$arg2}, double @var{$arg3})
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This probe is triggered when the @code{atan} function is called with
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an input that results in multiple precision computation. Argument
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@var{$arg1} is the precision with which computation succeeded.
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Argument @var{$arg2} is the input to the @code{atan} function and
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@var{$arg3} is the computed result.
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@end deftp
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@deftp Probe slowatan_inexact (int @var{$arg1}, double @var{$arg2}, double @var{$arg3})
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This probe is triggered when the @code{atan} function is called with
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an input that results in multiple precision computation and none of
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the multiple precision computations result in an accurate result.
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Argument @var{$arg1} is the maximum precision with which computations
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were performed. Argument @var{$arg2} is the input to the @code{atan}
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function and @var{$arg3} is the computed result.
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@end deftp
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@deftp Probe slowtan (double @var{$arg1}, double @var{$arg2})
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This probe is triggered when the @code{tan} function is called with an
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input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function and @var{$arg2}
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is the computed result.
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@end deftp
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@deftp Probe slowasin (double @var{$arg1}, double @var{$arg2})
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This probe is triggered when the @code{asin} function is called with
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an input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function and @var{$arg2}
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is the computed result.
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@end deftp
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@deftp Probe slowacos (double @var{$arg1}, double @var{$arg2})
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This probe is triggered when the @code{acos} function is called with
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an input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function and @var{$arg2}
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is the computed result.
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@end deftp
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@deftp Probe slowsin (double @var{$arg1}, double @var{$arg2})
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This probe is triggered when the @code{sin} function is called with an
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input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function and @var{$arg2}
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is the computed result.
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@end deftp
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@deftp Probe slowcos (double @var{$arg1}, double @var{$arg2})
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This probe is triggered when the @code{cos} function is called with an
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input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function and @var{$arg2}
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is the computed result.
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@end deftp
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@deftp Probe slowsin_dx (double @var{$arg1}, double @var{$arg2}, double @var{$arg3})
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This probe is triggered when the @code{sin} function is called with an
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input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function, @var{$arg2} is
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the error bound of @var{$arg1} and @var{$arg3} is the computed result.
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@end deftp
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@deftp Probe slowcos_dx (double @var{$arg1}, double @var{$arg2}, double @var{$arg3})
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This probe is triggered when the @code{cos} function is called with an
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input that results in multiple precision computation with precision
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32. Argument @var{$arg1} is the input to the function, @var{$arg2} is
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the error bound of @var{$arg1} and @var{$arg3} is the computed result.
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@end deftp
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@node Non-local Goto Probes
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@section Non-local Goto Probes
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These probes are used to signal calls to @code{setjmp}, @code{sigsetjmp},
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@code{longjmp} or @code{siglongjmp}.
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@deftp Probe setjmp (void *@var{$arg1}, int @var{$arg2}, void *@var{$arg3})
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This probe is triggered whenever @code{setjmp} or @code{sigsetjmp} is
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called. Argument @var{$arg1} is a pointer to the @code{jmp_buf}
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passed as the first argument of @code{setjmp} or @code{sigsetjmp},
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@var{$arg2} is the second argument of @code{sigsetjmp} or zero if this
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is a call to @code{setjmp} and @var{$arg3} is a pointer to the return
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address that will be stored in the @code{jmp_buf}.
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@end deftp
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@deftp Probe longjmp (void *@var{$arg1}, int @var{$arg2}, void *@var{$arg3})
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This probe is triggered whenever @code{longjmp} or @code{siglongjmp}
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is called. Argument @var{$arg1} is a pointer to the @code{jmp_buf}
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passed as the first argument of @code{longjmp} or @code{siglongjmp},
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@var{$arg2} is the return value passed as the second argument of
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@code{longjmp} or @code{siglongjmp} and @var{$arg3} is a pointer to
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the return address @code{longjmp} or @code{siglongjmp} will return to.
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|
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The @code{longjmp} probe is triggered at a point where the registers
|
|
have not yet been restored to the values in the @code{jmp_buf} and
|
|
unwinding will show a call stack including the caller of
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|
@code{longjmp} or @code{siglongjmp}.
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@end deftp
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@deftp Probe longjmp_target (void *@var{$arg1}, int @var{$arg2}, void *@var{$arg3})
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This probe is triggered under the same conditions and with the same
|
|
arguments as the @code{longjmp} probe.
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|
|
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The @code{longjmp_target} probe is triggered at a point where the
|
|
registers have been restored to the values in the @code{jmp_buf} and
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|
unwinding will show a call stack including the caller of @code{setjmp}
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|
or @code{sigsetjmp}.
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|
@end deftp
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