Fix syslog mutual exclusion and interrupt level logic
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4999 42af7a65-404d-4744-a932-0658087f49c3
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patacongo
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@ -4101,6 +4101,7 @@ build
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<li>
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<code>CONFIG_SYSLOG_CHAR</code>:
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Enable the generic character device for the SYSLOG.
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A disadvantage of using the generic character device for the SYSLOG is that it cannot handle debug output generated from interrupt level handlers.
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NOTE: No more than one SYSLOG device should be configured.
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<p>
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Alternatively, a circular buffer in RAM can be used as the SYSLOGing device.
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@ -4118,11 +4119,11 @@ build
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circular buffer and can be viewed using the NSH 'dmesg' command.
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</li>
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<li>
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<code>CONFIG_RAMLOG_SYSLOG</code>: Use the RAM logging device for the syslogging
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interface. If this feature is enabled (along with <code>CONFIG_SYSLOG</code>),
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then all debug output (only) will be re-directed to the circular
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buffer in RAM. This RAM log can be view from NSH using the 'dmesg'
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command.
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<code>CONFIG_RAMLOG_SYSLOG</code>:
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Use the RAM logging device for the syslogging interface.
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If this feature is enabled (along with <code>CONFIG_SYSLOG</code>), then all debug output (only) will be re-directed to the circular buffer in RAM.
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This RAM log can be view from NSH using the <code>dmesg</code> command.
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NOTE: Unlike the limited, generic character driver SYSLOG device, the RAMLOG <i>can</i> be used to generate debug output from interrupt level handlers.
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</li>
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<li>
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<code>CONFIG_RAMLOG_NPOLLWAITERS</code>: The number of threads than can be waiting
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@ -381,6 +381,8 @@ defconfig -- This is a configuration file similar to the Linux
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is selected, then these options are also available.
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CONFIG_SYSLOG_CHAR - Enable the generic character device for the SYSLOG.
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A disadvantage of using the generic character device for the SYSLOG is that
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it cannot handle debug output generated from interrupt level handlers.
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NOTE: No more than one SYSLOG device should be configured.
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CONFIG_RAMLOG - Enables the RAM logging feature. The RAM log is a circular
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@ -395,7 +397,9 @@ defconfig -- This is a configuration file similar to the Linux
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interface. If this feature is enabled (along with CONFIG_SYSLOG),
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then all debug output (only) will be re-directed to the circular
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buffer in RAM. This RAM log can be view from NSH using the 'dmesg'
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command.
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command. NOTE: Unlike the limited, generic character driver SYSLOG
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device, the RAMLOG *can* be used to generate debug output from interrupt
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level handlers.
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CONFIG_RAMLOG_NPOLLWAITERS - The number of threads than can be waiting
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for this driver on poll(). Default: 4
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@ -14,10 +14,16 @@ syslog_putc().
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One version of syslog_putc() is defined in fs/fs_syslog.c; that version is
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used when CONFIG_SYSLOG_CHAR is defined. That version of syslog_putc()
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just integrates with the file system to re-direct debug output to a
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character device or to a file.
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character device or to a file. A disadvantage of using the generic character
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device for the SYSLOG is that it cannot handle debug output generated from
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interrupt level handles.
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If CONFIG_SYSLOG_CHAR is not defined, then other custom SYSLOG drivers
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can be used. Those custom SYSLOG drivers reside in this directory.
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can be used. These custom SYSLOG drivers can do things like handle
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unusual logging media and since they can avoid the general file system
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interfaces, can be designed to support debug output from interrupt handlers.
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Those custom SYSLOG drivers reside in this directory.
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ramlog.c
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--------
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@ -46,7 +52,9 @@ ramlog.c
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interface. If this feature is enabled (along with CONFIG_SYSLOG),
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then all debug output (only) will be re-directed to the circular
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buffer in RAM. This RAM log can be view from NSH using the 'dmesg'
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command.
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command. NOTE: Unlike the limited, generic character driver SYSLOG
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device, the RAMLOG *can* be used to generate debug output from interrupt
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level handlers.
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CONFIG_RAMLOG_NPOLLWAITERS - The number of threads than can be waiting
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for this driver on poll(). Default: 4
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131
fs/fs_syslog.c
131
fs/fs_syslog.c
@ -49,6 +49,7 @@
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#include <assert.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/arch.h>
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#include <nuttx/syslog.h>
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#include "fs_internal.h"
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@ -66,6 +67,10 @@
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#define SYSLOG_OFLAGS (O_WRONLY | O_CREAT | O_APPEND)
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/* An invalid thread ID */
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#define NO_HOLDER ((pid_t)-1)
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/****************************************************************************
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* Private Types
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****************************************************************************/
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@ -75,7 +80,7 @@
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enum syslog_state_e
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{
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SYSLOG_UNINITIALIZED = 0, /* SYSLOG has not been initialized */
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SYSLOG_BUSY, /* SYSLOG is not available for this thread */
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SYSLOG_INITIALIZING, /* SYSLOG is being initialized */
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SYSLOG_REOPEN, /* SYSLOG open failed... try again later */
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SYSLOG_FAILURE, /* SYSLOG open failed... don't try again */
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SYSLOG_OPENED, /* SYSLOG device is open and ready to use */
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@ -87,6 +92,7 @@ struct syslog_dev_s
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{
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uint8_t sl_state; /* See enum syslog_state_e */
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sem_t sl_sem; /* Enforces mutually exclusive access */
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pid_t sl_holder; /* PID of the thread that holds the semaphore */
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struct file sl_file; /* The syslog file structure */
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};
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@ -107,6 +113,69 @@ static const uint8_t g_syscrlf[2] = { '\r', '\n' };
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: syslog_takesem
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*
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* Description:
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* Write to the syslog device
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*
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****************************************************************************/
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static inline int syslog_takesem(void)
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{
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pid_t me = getpid();
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int ret;
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/* Does this thread already hold the semaphore? That could happen if
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* we wer called recursively, i.e., if the logic kicked off by
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* syslog_write() where to generate more debug output. Return an error
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* in that case.
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*/
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if (g_sysdev.sl_holder == me)
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{
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/* Return an error (instead of deadlocking) */
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return -EWOULDBLOCK;
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}
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/* Either the semaphore is available or is currently held by another
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* thread. Wait for it to become available.
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*/
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ret = sem_wait(&g_sysdev.sl_sem);
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if (ret < 0)
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{
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return -get_errno();
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}
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/* We hold the semaphore. We can safely mark ourself as the holder
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* of the semaphore.
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*/
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g_sysdev.sl_holder = me;
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return OK;
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}
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/****************************************************************************
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* Name: syslog_givesem
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*
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* Description:
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* Write to the syslog device
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*
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****************************************************************************/
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static inline void syslog_givesem(void)
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{
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pid_t me = getpid();
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DEBUGASSERT(g_sysdev.sl_holder == me);
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/* Relinquish the semaphore */
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g_sysdev.sl_holder = NO_HOLDER;
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sem_post(&g_sysdev.sl_sem);
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}
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/****************************************************************************
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* Name: syslog_write
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*
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@ -172,13 +241,13 @@ int syslog_initialize(void)
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int ret;
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/* At this point, the only expected states are SYSLOG_UNINITIALIZED or
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* SYSLOG_REOPEN.. Not SYSLOG_BUSY, SYSLOG_FAILURE, SYSLOG_OPENED.
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* SYSLOG_REOPEN.. Not SYSLOG_INITIALIZING, SYSLOG_FAILURE, SYSLOG_OPENED.
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*/
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DEBUGASSERT(g_sysdev.sl_state == SYSLOG_UNINITIALIZED ||
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g_sysdev.sl_state == SYSLOG_REOPEN);
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g_sysdev.sl_state = SYSLOG_BUSY;
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g_sysdev.sl_state = SYSLOG_INITIALIZING;
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/* Try to open the device.
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*
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@ -272,7 +341,8 @@ int syslog_initialize(void)
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/* The SYSLOG device is open and ready for writing. */
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sem_init(&g_sysdev.sl_sem, 0, 1);
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g_sysdev.sl_state = SYSLOG_OPENED;
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g_sysdev.sl_holder = NO_HOLDER;
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g_sysdev.sl_state = SYSLOG_OPENED;
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return OK;
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errout_with_inode:
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@ -300,27 +370,33 @@ int syslog_putc(int ch)
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/* Ignore any output:
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*
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* (1) Before the SYSLOG device has been initialized. This could happen
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* from debug output that occurs early in the boot sequence before
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* syslog_initialize() is called (SYSLOG_UNINITIALIZED_.
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* (2) While the device is being initialized. The case could happen if
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* debug output is generated while syslog_initialize() executes
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* (SYSLOG_BUSY).
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* (2) While we are generating SYSLOG output. The case could happen if
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* debug output is generated while syslog_putc() executes (also
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* SYSLOG_BUSY).
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* (1) Before the SYSLOG device has been initialized. This could happen
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* from debug output that occurs early in the boot sequence before
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* syslog_initialize() is called (SYSLOG_UNINITIALIZED).
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* (2) While the device is being initialized. The case could happen if
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* debug output is generated while syslog_initialize() executes
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* (SYSLOG_INITIALIZING).
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* (3) While we are generating SYSLOG output. The case could happen if
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* debug output is generated while syslog_putc() executes
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* (This case is actually handled inside of syslog_semtake()).
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* (4) Any debug output generated from interrupt handlers. A disadvantage
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* of using the generic character device for the SYSLOG is that it
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* cannot handle debug output generated from interrupt level handlers.
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* (5) If an irrecoverable failure occurred during initialization. In
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* this case, we won't ever bother to try again (ever).
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*
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* NOTE: That the third case is different. It applies only to the thread
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* that currently holds the sl_sem sempaphore. Other threads should wait.
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* that is why that case is handled in syslog_semtake().
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*/
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if (g_sysdev.sl_state == SYSLOG_UNINITIALIZED ||
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g_sysdev.sl_state == SYSLOG_BUSY)
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g_sysdev.sl_state == SYSLOG_INITIALIZING ||
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up_interrupt_context())
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{
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return -EAGAIN;
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}
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/* If an irrecoverable failure occurred, then don't bother to try again
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* (ever)
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*/
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if (g_sysdev.sl_state == SYSLOG_FAILURE)
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{
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return -ENXIO;
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@ -369,18 +445,20 @@ int syslog_putc(int ch)
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* value to write.
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*/
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ret = sem_wait(&g_sysdev.sl_sem);
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ret = syslog_takesem();
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if (ret < 0)
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{
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return -get_errno();
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/* We probably already hold the semaphore and were probably
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* re-entered by the logic kicked off by syslog_write().
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* We might also have been interrupted by a signal. Either
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* way, we are outta here.
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*/
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return ret;
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}
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/* Pre-pend a newline with a carriage return. Setting sl_state to
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* SYSLOG_BUSY will suppress any recursive debug logic generated by
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* the syslog_write call.
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*/
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/* Pre-pend a newline with a carriage return. */
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g_sysdev.sl_state == SYSLOG_BUSY;
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if (ch == '\n')
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{
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/* Write the CR-LF sequence */
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@ -405,8 +483,7 @@ int syslog_putc(int ch)
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nbytes = syslog_write(&ch, 1);
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}
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g_sysdev.sl_state == SYSLOG_OPENED;
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sem_post(&g_sysdev.sl_sem);
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syslog_givesem();
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/* Check if the write was successful */
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@ -73,7 +73,9 @@
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* interface. If this feature is enabled (along with CONFIG_SYSLOG),
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* then all debug output (only) will be re-directed to the circular
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* buffer in RAM. This RAM log can be view from NSH using the 'dmesg'
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* command.
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* command. NOTE: Unlike the limited, generic character driver SYSLOG
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* device, the RAMLOG *can* be used to generate debug output from interrupt
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* level handlers.
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* CONFIG_RAMLOG_NPOLLWAITERS - The number of threads than can be waiting
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* for this driver on poll(). Default: 4
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*
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@ -59,7 +59,9 @@
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* described in the include/nuttx/ramlog.h header file.
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*
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* 2. And a generic character device that may be used as the SYSLOG. The
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* generic device interfaces are described in this file.
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* generic device interfaces are described in this file. A disadvantage
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* of using the generic character device for the SYSLOG is that it
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* cannot handle debug output generated from interrupt level handlers.
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*
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* CONFIG_SYSLOG_CHAR - Enable the generic character device for the SYSLOG.
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* The full path to the SYSLOG device is provided by CONFIG_SYSLOG_DEVPATH.
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