STRTOD(3)           Linux Programmer's Manual           STRTOD(3)




NAME

       strtod - convert ASCII string to double


SYNOPSIS

       #include <stdlib.h>

       double strtod(const char *nptr, char **endptr


DESCRIPTION

       The  strtod  function  converts the initial portion of the
       string pointed to by nptr to double representation.

       The expected form  of  the  string  is  an  optional  plus
       (``+'')  or  minus  sign (``-'') followed by a sequence of
       digits optionally containing  a  decimal-point  character,
       optionally  followed by an exponent.  An exponent consists
       of an ``E'' or ``e'', followed  by  an  optional  plus  or
       minus sign, followed by a sequence of digits.

       Leading  white-space  characters in the string (as defined
       by the isspace(3) function) are skipped.


RETURN VALUES

       The strtod function returns the converted value, if any.

       If endptr is not NULL, a pointer to  the  character  after
       the last character used in the conversion is stored in the
       location referenced by endptr.

       If no conversion is performed, zero is  returned  and  the
       value  of  nptr  is  stored  in the location referenced by
       endptr.

       If the correct value would cause overflow, plus  or  minus
       HUGE_VAL is returned (according to the sign of the value),
       and ERANGE is stored in errno.  If the correct value would
       cause  underflow, zero is returned and ERANGE is stored in
       errno.


ERRORS

       ERANGE Overflow or underflow occurred.

SEE ALSO

atof, atoi, atol, strtol, strtoul, 



STANDARDS

       The strtod function conforms to ANSI-C.


BUGS

       This is a BSD manual page and may not reflect the  current
       Linux implementation.







BSD Man Page               21 Aug 1994                          1

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authorDouglas Miller <dougmill@linux.vnet.ibm.com>2017-01-28 06:42:20 -0600
committerTejun Heo <tj@kernel.org>2017-01-28 07:49:42 -0500
commit966d2b04e070bc040319aaebfec09e0144dc3341 (patch)
tree4b96156e3d1dd4dfd6039b7c219c9dc4616da52d /tools/perf/tests/attr/test-stat-detailed-3
parent1b1bc42c1692e9b62756323c675a44cb1a1f9dbd (diff)
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'tools/perf/tests/attr/test-stat-detailed-3')